A question I get asked on just about all of the projects I build is, “what’s the best insulation to use?” It’s a fair question, and with more choice than ever, and a lot of it marketed as being higher performance, more sustainable, or somehow smarter than what came before, it's hard to know what is actually best.

The honest answer is that there isn’t a single “best” option. The way we build with insulation has changed massively in recent years.

It’s no longer just about thermal performance defined by a data sheet. It’s now about how materials behave in real buildings, how they’re installed, and how they’ll be durable and reliable over the life of a building.

Why insulation innovations are needed

The process of specifying an insulation product looks straightforward. You meet your U- values under Part L of the building regulations, by selecting an insulation of the appropriate thickness, and then demonstrate compliance through a plethora of assessments including U-value calculations, condensation risk analysis and SAP assessments.

This process is fine on paper, but in reality, insulation performs very differently depending on the conditions it's installed in. For example, warm air carries moisture, and this moisture can move through the building fabric, through gaps, junctions and service penetrations. When it meets a cold surface, it condenses, which is where problems start.

As a result, the new generation of insulation products is starting to focus much more on buildability and issues such as moisture management, which can adversely affect an insulation's thermal performance, as well as damaging building structures.

Breathable construction methods and bio-based insulation

One of the more interesting developments has been the rise of bio-based insulation, particularly products made from hemp and recycled fibres like jute.

Insulation products such as IndiTherm and IndiBreathe Flex are starting to be used on self-build projects, especially where self-builders are concerned about sustainability. Whilst they are using eco insulation such as hemp and recycled fibres to reduce embodied carbon, the broader appeal of these products is how they deal with moisture.

Natural insulation materials such as hemp and wood fibre are hygroscopic. This means that they can absorb moisture and release it again, without deteriorating or significantly affecting their performance. Instead of trapping moisture within a wall or roof, they allow it to breathe and dissipate moisture. This doesn’t mean that a vapour control or airtightness membrane isn’t needed, but it does mean that the building structure has a better chance of drying out if something isn’t quite right.

With traditional, impermeable insulation boards such as EPS, PIR or Phenolic boards, if moisture isn’t properly managed it can get trapped. With natural fibre insulation, there’s a bit more tolerance which makes it more forgiving.

There’s also a school of thought that when a building is insulated with natural insulation, you’ll get a better internal environment. The suggestion is that homes insulated in this way feel less 'sealed', with humidity levels more stable. The result is less condensation, and a healthier internal environment that’s not affected by synthetic-based insulation products.

Alongside hemp and jute, products like Steico wood fibre boards and HempKor systems are also gaining traction. They work on similar principles – breathable, vapour open, and better at managing moisture within the building structure.

This all sounds great, but there are downsides to consider. Natural insulation products tend to require thicker build-ups to achieve the same U-values as high-performance synthetic boards. This has implications for wall thickness, architectural detailing and space.

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Improving traditional materials with bio-based binders

Not every project is suited to fully bio-based insulation, and many still rely on more conventional materials like glass wool.

What’s encouraging is that these materials are evolving. Manufacturers have started replacing traditional petrochemical binders with lignin-based alternatives which are derived from forestry by-products.

From a site perspective, nothing changes. It installs in the same way, and performs as expected. But the use of environmentally friendly binders is a step in the right direction that reduces our carbon footprint and reliance on fossil fuels.

Advances in high-performance insulation

There are still situations where you need maximum performance in minimal space. This is where high-end insulation products become essential.

Insulation products like Kingspan’s low lambda Kooltherm are widely used because they achieve very low U-values, with relatively thin build ups. In tight urban sites, or where you’re trying to maximise internal floor area, these products can become essential.

In recent years, products like Optim-R, which is a vacuum insulation panel, have pushed slimness even further. While they are eye-wateringly expensive, they are genuinely innovative, and solve problems that other insulation products can’t, such as insulating balconies where threshold details are tight.

While VIP insulation is undeniably innovative, it's not without its drawbacks. Aside from the expense, these products require careful handling, and can’t be cut or modified on site. Damage them and their performance drops significantly, which means they must be handled carefully. They’re also less forgiving in terms of moisture behaviour, so detailing and moisture management is essential.

B&Q currently stock a range of Kingspan Kooltherm insulation boards.

Robotic underfloor insulation

Suspended timber floors are a classic insulation problem area. They’re common in older homes, and insulating them properly is notoriously difficult. Access is limited, working conditions poor, and it’s very easy to miss areas. The result is cold floors, draughts, and a house that’s hard to keep warm.

Systems like Q-Bot have been developed to address this problem. Instead of sending installers under a floor, a small robot is used to apply spray insulation to the underside of the floor which would normally be difficult to reach.

The result is less disruption, a warmer floor with fewer draughts and a noticeable improvement in comfort. While this improves energy efficiency, it also reduces air movement through the floor, so careful design is needed to manage condensation risks.

What building control looks for with new insulation methods

Whilst the building regulations documents set the rules for compliance, building control officers also focus on how a building will perform in reality.

To ensure that a building is energy efficient and safe to live in, they’ll look at what insulation products have been used, and whether they’ve been installed as per the design. Key areas of focus are continuity of insulation, risk of thermal bridging and how moisture is being managed. They’ll also ask for U-values calculations and condensation risk analysis, just to make sure that the products have been properly considered and meet the required standards.

While the same rules will apply to new insulation products, as officers will be familiar with widely used standard insulation products, when it comes to newer and innovative approaches, they’ll likely need a little more convincing before signing off the approach.

Finding the right balance between old and new

For most self-builders, the challenge isn’t choosing the most advanced insulation system. It’s putting together a combination that works for the building, the construction team and still fits within the budget. This means understanding how to achieve a specific level of performance, while balancing the practicalities of installation, airtightness and moisture management.

In my experience, the best results come from a balanced approach. Using breathable materials where moisture risk is higher, high-performance boards where space is limited and always making sure that installation is carried out properly.

Insulation isn’t just about keeping heat in, it’s also about making sure that the building works – not just at completion, but for years to come.

For more in-depth advice on insulating your home, take a look at how long insulation lasts to see if this will impact your purchasing decisions, and how much insulation costs could be to help you plan your budget accordingly.

Most people don’t give much thought to insulating between floors – at least not until it becomes a problem. The thud of footsteps, noisy TVs and the pitter patter of someone having a shower. The fix is often seen as simple – thick carpets, maybe more insulation, or learn to live with the nuisance.

The reality is a bit more nuanced than that, and intermediate floor insulation installed correctly will deal with three problems at once. It reduces sound transfer between floors, slows the spread of fire through the structure, and helps control how heat moves around the house.

If you don’t understand what intermediate floor insulation does, it’s easy to spend money without really solving the problem, but the way you approach it starts with understanding the problems at hand.

The noise problem

Historically, most traditionally built older homes in the UK have a timber intermediate floor between storeys. Timber joists span from wall-to-wall, with floorboards or chipboard on top, and plasterboard ceilings underneath.

This leaves a hollow void which can act like a drum. Sound resonates within the void, amplifying footsteps, voices and music. If the floorboards are slightly loose, or there are gaps around the edges, the noise problem gets worse.

There are two distinct types of noise at play here, and both behave very differently.

• Airborne noise – This is what you hear when someone is talking upstairs or a television is on. It travels through the air and into the structure. The best way to deal with it is by adding insulation to absorb and disrupts sound waves, which would pass through the void.
• Impact noise is different – This is the sharp, physical transmission of energy through the structure: footsteps, dropped objects, kids running across a bedroom. You can almost feel the noise just as much as hear it. This is where people often get caught out, because stuffing insulation between joists does very little to stop it.

Fire safety

The building regulations and Approved Document B, set out the requirements for fire resistance between floors, and as such, fire-stopping between floors is often treated as a building regs compliance issue.

But as timber intermediate floors typically have the least level of fire integrity of any building element, compromising the fire integrity of an intermediate floor has real-world consequences.

Whilst the correct selection of materials, and filling the floor void with non-combustible insulation will help to slow fire spread, gaps are a weak point. Any openings around pipes, cables or at the edges of floors can allow fire to bypass the insulation layer entirely. Fire-stopping products and careful sealing around penetrations are essential, and where attention to detail matters.

In reality, building control officers tend to focus on whether the overall construction provides adequate protection, rather than the specific insulation product used. While this gives some flexibility, it also means responsibility sits with the designer and installer to get the details right. Therefore always consult a competent designer before making any alterations that may impair fire performance.

Insulating intermediate floors

It’s worth being clear that insulating intermediate floors is a very different exercise from insulating a ground floor in older houses.

Ground floors are primarily about controlling heat loss and managing moisture, particularly in suspended timber floors where ventilation is critical to avoid damp and decay.

Intermediate floors, on the other hand, are more about comfort and separation. You’re not dealing with ground moisture or significant heat loss, but with sound transfer, fire protection and internal heat movement.

This changes the priorities, and in intermediate floors, acoustic performance and airtightness often matter much more than thermal resistance.

Insulation options for intermediate floors

The joist void offers the main opportunity to improve performance, particularly in retrofit situations. And provided the work is done properly, it offers an easy win.

Mineral wool or glass wool insulation is typically used here. It’s relatively inexpensive, non-combustible, and dense enough to absorb airborne sound effectively. When fitted correctly between joists, it provides an acoustic break within the empty cavity that would otherwise allow sound to resonate through.

Sounds simple but for the insulation to be able to perform, it needs to sit snugly between joists without being compressed. If it’s squashed around pipes or cables, its performance drops. Equally, if it’s loosely fitted, it won’t do its job properly as air gaps will completely undermine its effectiveness. So don't make this insulation mistake.

Another detail that often gets overlooked is support. Insulation in floors that need to be suspended must be properly supported, typically using netting or timber battens. Without support, insulation will sag over time, creating gaps where sound can penetrate.

It's also worth remembering that electrical cables running through insulation can overheat if they’re completely surrounded. While this isn’t a problem in new homes, older circuits may not have the same current-carrying capacity as modern cables. This doesn’t mean you can’t insulate a floor void, it just means it needs to be done with a bit of care, especially in older properties.

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Insulating from above

If you have the option, insulating from above when insulating between floors is the easiest approach, depending on how the floor has been constructed. Working from above usually means lifting floorboards or removing chipboard decking, which isn’t always possible or convenient, especially if the boards are glued down, or walls are built off them.

If the floor can be lifted, insulation can be cut and fitted tightly between joists with no gaps. And, whilst the floor is up, it’s also possible to deal with another acoustic issue – air gaps.

Gaps around the perimeter of the floor, between floorboards, or where pipes pass through, allow air to move freely between floor levels. This airflow carries both heat and sound, bypassing whatever insulation is installed. Sealing these gaps with insulation, or a flexible acoustic sealant will make a noticeable difference.

Once the floorboards are back in place and sealed up, impact noise can be dealt with. This is where acoustic underlays are popular, with layers of rubber, foam or felt installed beneath the final floor finish. This creates a resilient layer that absorbs the energy of footsteps before it enters the structure.

Insulating from below

Where lifting floors isn’t practical, the only real option is to work from below, which usually requires the ceilings to be replaced.

With the plasterboard ceilings removed, insulation can be installed between the joists before new plasterboard is fixed. It’s a destructive and disruptive process, but possibly the only way to properly retrofit floor insulation.

When taking this approach, it’s worth upgrading the plasterboard ceiling to a different type of plasterboard with better acoustic, or fire performance properties. Acoustic plasterboard, or even doubling up on plasterboard layers will significantly improve airborne sound reduction. Fire-rated plasterboard is also worth considering, particularly in two-storey homes where separating floors form part of the fire strategy.

Insulating a floor from below doesn’t address impact noise in the same way as working from above, so acoustic underlays may still be required.

Choosing the right materials

The correct material choice isn’t about finding a miracle product, but is more about understanding what each material does well.

Mineral wool insulation and glass wool remain the go-to options for most inter-floor insulation. They strike a good balance between how much insulation costs, fire resistance and acoustic performance. High-density acoustic mineral wool products go a step further, offering better sound absorption due to their increased mass, but are without doubt harder to install, especially around existing services.

For impact noise, acoustic underlays are designed specifically to absorb vibration. These sit directly beneath floor finishes such as laminate, engineered timber or even carpet. Whilst specialist acoustic floor systems are available, these are rather technical, expensive and not easy to retrofit within an existing house, especially where headroom is limited.

The key point when choosing materials is that no single material solves everything. In practice, good results come from combining layers, filling mass within floor voids, installing acoustic resilience at the surface, and achieving airtightness with a good level of workmanship.

Insulating between floors is one of those jobs where small details make a big difference. It’s not complicated and is often one of the best ways to insulate a home, but it’s easy to get wrong.

Over the years I’ve seen many projects, and even new build ones where expensive materials were installed poorly and delivered very little performance. I’ve also seen relatively simple upgrades such as well-fitted mineral wool, combined with decent airtightness transform how a house feels.

In my experience, getting things right requires a focus on the system as a whole, and not just the insulation. Think about how sound, air and heat move through the floor, and deal with each of them, not forgetting that exceptional standards of workmanship and quality are essential to achieve the desired outcome.

Four people have been arrested as part of a £44m fraud investigation linked to the Energy Company Obligation (ECO4) scheme.

Although the scheme, which required energy suppliers to fund home insulation and heating upgrades for lower-income households, has now closed, investigators believe some firms may have claimed payment for work that was never completed.

The case adds to the growing scrutiny of retrofit insulation programmes in recent years.

What the £44m fraud investigation is about

The Serious Fraud Office (SFO), working with the National Crime Agency, carried out coordinated raids across England, arresting four individuals on suspicion of conspiracy to defraud.

The investigation centres on claims that companies submitted invoices for insulation work under ECO4 that was either not carried out or only partially completed.

Numerous other firms are being examined in connection with contracts between 2022 and 2024. Authorities believe energy suppliers may have been defrauded of up to £44m through false or inflated claims.

SFO director Graham McNulty said: “This scheme was designed to reduce carbon emissions, help households cut costs and stay warm – instead, in many cases we suspect little or no work was done.”

Wider concerns over insulation schemes

The ECO4 programme has previously faced criticism for repeated failures, including inconsistent installation quality, poor workmanship, and limited oversight across a fragmented supply chain of contractors and subcontractors.

Industry commentary and homeowner reports have highlighted cases of insulation being fitted incorrectly, unsuitable measures being installed, and disputes over whether work met required standards.

MPs have also raised concerns in recent years about how effectively schemes like ECO4 were monitored, particularly given the number of separate organisations involved in delivery and compliance checks.

What happens next

The investigation forms part of a wider crackdown on economic crime, with authorities urging installers, assessors and others involved in ECO4 projects to come forward with information.

Solicitor General Ellie Reeves said: “This scheme was meant to tackle fuel poverty and improve people’s homes. I am sickened by those who want to profit off the back of a scheme designed to help vulnerable people, and I’m confident the SFO’s investigation into allegations of substantial fraud will deliver the answers victims and the public deserve.”

The ECO4 scheme has now ended and is being replaced by the government’s Warm Homes Plan, which will continue funding energy efficiency upgrades such as insulation, solar panels and heat pumps.

Most houses, particularly those built some time ago, throw up a few niggles from time to time – damp, draughts, creaky floorboards and so on. While some are pretty harmless, if you've found cold spots on internal walls within your home, you definitely need to pay attention.

"Cold spots are more than just inconvenient; they’re often a sign of underlying problems in your building’s thermal envelope – the barrier that separates your indoor space from the outside environment," explains Ryan Jones, head of testing at Building Energy Experts.

To help you get to the bottom of why cold spots might be appearing and what to do about it, we reached out to the experts – thankfully there are steps you can take to rectify the problem once and for all.

What do cold spots on walls mean?

If you have stumbled across a cold patch (or more than one), it is important to understand what caused it.

"A cold patch on a wall means that part of the building is losing heat faster than the rest," picks up Michael Zohouri, founder at Pyramid Eco. "That’s down to poor insulation or thermal bridging, where heat escapes more easily through certain parts of the wall.

"It’s something you see quite often in older properties, especially around windows, on external walls and in corners of rooms," continues Michael. "In some cases it’s just an area where insulation is missing or thinner than it should be."

Ryan Jones reveals a few more causes of cold spots. "Moisture build-up can compromise insulation, structural issues can create thermal bridges (areas where heat transfers more readily) and plumbing issues, such as leaking pipes behind walls or under floors, can introduce cold water into the space."

How do you find cold spots on walls?

Unless you are happy to walk around your whole house feeling every inch of the walls for cold spots, these can sometimes go undetected. Thankfully, there are other ways of finding them, including looking into the various building surveys available to homeowners.

"You don’t need to rely on guesswork to identify these problem areas," says Ryan Jones. "There are home energy survey methods to identify weaknesses in your building envelope. For example, our thermal imaging survey can detect temperature variations, highlighting cold spots and underlying issues, and our air tightness test measures uncontrolled air leakage, identifying draughts and other energy-wasting gaps in your building."

Are cold spots on walls something to worry about?

Clearly, then, cold spots on walls are an indication that something is not quite right – but what can happen if you simply ignore them?

"Ignoring these issues can lead to drafts and uneven temperatures," warns Ryan Jones. "Cold spots disrupt the overall heating and cooling efficiency, leading to uncomfortable drafts and uneven temperatures. Your HVAC (heating, ventilation and air conditioning) systems have to work overtime to combat heat loss, driving up your energy costs. Cold spots also lead to condensation, creating ideal conditions for mould."

Michael Zohouri agrees that to turn a blind eye to cold spots is a mistake.

"The biggest risk is mould," warns Michael. "Once condensation starts forming regularly on a cold patch, mould spores can take hold quite quickly. It can also mean higher heating bills. If part of the building envelope is losing heat, your heating system has to work harder to keep the room comfortable."

How do you get rid of cold spots on walls?

No doubt once you have discovered any cold spots you will be pretty keen to deal with them before they start causing you too many issues.

"The solution depends on the cause of the problem," picks up Michael Zohouri. "The first thing I would check is insulation. You might find there is no insulation or only a thin layer that’s degraded. Loft insulation, cavity wall insulation or insulated plasterboard can all help raise the surface temperature of the wall.

"Air leaks can also cause cold spots," continues Michael. "Check for any gaps around windows or pipework that could be allowing cold air into the structure. Sealing those gaps can reduce cold patches.

"In some cases your furniture placement in the room could be the problem," adds Michael. "So, if there’s a large wardrobe or a sofa pushed up against an external wall it stops air circulating. That keeps the area colder increases condensation risk. Leaving a small gap behind furniture helps air move around the wall."

FAQs

How do you check wall insulation?

A well-insulated home is far less likely to suffer from cold spots and subsequent condensation and mould problems, but it can be hard to know what your insulation levels are like, particularly in older properties.

If your home was built after 1920 it is likely to have cavity walls which will hopefully be insulated. You can also get an idea of whether your home has cavity walls by measuring the depth of a wall by a window or door – if it is over 260mm it will probably have a cavity. Be on the lookout for small boreholes in the external brickwork too as these are a good indicator that cavity wall insulation will have been fitted at some point.

Of course, if your home has solid walls things get a little tricky. Unless you want to add internal wall insulation, which means losing some floor space, your other option is to add external wall insulation which is where things can get a little pricey as you will need to reclad the exterior of your home.

DIY testing for insulation is possible using something like this Endoscope Inspection Camera from Amazon. However, for a more accurate picture of your home's insulation, a professional inspection is recommended.

If you have discovered mould has already taken hold due the cold spots in your home, don't panic. In many cases mould removal can be carried out on a DIY basis – the key is to treat it as soon as it appears.

Walk into a basement and you’ll probably feel a familiar chill. Not a draught exactly, but a cool and often dank feeling, despite the heating being on full. This feeling is usually down to the surface temperature of the basement and a sign that it would benefit from being insulated.

Insulating a building below ground is fundamentally different from insulating a building above it. Basement walls and floors are in constant contact with the ground, which keeps them relatively cool all year round. Without proper insulation, the walls and floors of your basement design will draw heat out of a room, resulting in chilly surfaces, surface condensation and higher heating bills.

Most basements also experience some level of moisture from the surrounding ground. In the UK, where groundwater levels can be high and heavy rainfall is common, modern basement design often assumes that some water will eventually find its way through. Cavity drain membranes and sump pumps are therefore a common feature.

With all this in mind, insulating a basement requires a well thought through strategy that deals with the walls and floors using materials that can either tolerate damp conditions or be protected from moisture completely.

Insulating basement walls

When it comes to thermal comfort below ground, the walls tend to do most of the heavy lifting. They form the largest surface area, which means they’re also the biggest potential route for heat loss.

Part L of the Building Regulations sets the energy performance standards, including walls and floors. On a new-build project, while the target U value is around 0.18mW/m²K the actual performance is considered as part of the overall energy strategy and within the SAP calculation for the building.

In basement conversions the situation is slightly different. Space is often limited and the structure already exists, which means achieving the same insulation thickness as an above-ground wall is not always possible. In my experience building control officers tend to take a pragmatic view in these situations. They recognise the constraints and usually look for reasonable improvement somewhere around 0.30 W/m²K, provided there’s no condensation risk.

Insulating a basement floor

As with basement walls, a concrete slab sitting directly on the ground will steadily conduct heat away from the room if it isn’t insulated. This creates cold surfaces and increases the amount of heating needed to keep the room warm.

When considering your basement conversion ideas, bear in mind that the existing slab becomes a renovated thermal element once insulation and a new floor build-up are installed. This means building control will normally expect the upgraded floor to have a U value of 0.25 W/m²K.

Floor insulation can be installed below the slab, above it, or occasionally in both positions depending on the waterproofing strategy. In basement conversions insulation is usually added above the existing concrete slab, which creates a few practical challenges. Adding rigid insulation boards and a screed raises the finished floor level, which reduces headroom. Where headroom is tight, this can require adjustment of stair risers and door heads, which is often easier said than done.

What to consider before installing insulation

Meeting Part L requirements in a basement isn’t just about achieving a particular U-value. What building control officers usually want to see is a sensible insulation strategy that works alongside waterproofing and ventilation systems.

1. Ventilation

Basements are naturally cooler environments and warm air from the upper floors often drifts downwards carrying moisture with it. If that air reaches a cold surface it will condense. This is where ventilation becomes important.

As insulation levels improve, uncontrolled air leakage reduces so a basement will become more airtight. Whilst this is good for energy efficiency, it also means ventilation systems are required, especially in basement bathrooms, utility rooms or gyms.

2. Waterproofing

No insulation system will work properly if the structure itself is damp, so waterproofing is a critical starting point in any basement design and insulation strategy.

In the UK, three main approaches are used. Barrier protection relies on external tanking to keep water out entirely. Integral protection uses waterproof concrete that limits water penetration. Drained protection takes a different approach, using cavity membranes and sump pumps to manage water that enters the structure. In practice, many basements combine more than one method for added security.

Building control officers will ask questions when they see insulation being installed against basement structures that haven’t been adequately protected. So, always make sure the insulation system is properly designed and follow it to the letter.

Insulating a basement checklist

Whilst the main focus when insulating a basement are the walls and floor, the smaller details can have just as much impact so mustn’t be overlooked.

1. Making your insulation work with basement drainage

Many modern basements use what’s known as a Type C drained protection system. A cavity membrane is fixed to the inside face of the structural wall, creating a small drainage space. Any moisture that penetrates the structure is directed down the membrane into perimeter channels and then into a sump pump. The insulation and wall lining are then installed on the room side of this system. This is where things need to be thought through carefully. The entire system relies on water being able to move freely down the wall and away from the structure. Insulation must therefore never block the drainage path behind the membrane or be allowed to get wet. Fixings that pass through the membrane and the insulation therefore need to be properly sealed.

2. Avoiding thermal bridging with your insulation

Thermal bridging is an area where basement projects often run into trouble. Junctions between the wall and floor slab, structural beams and stair openings can all become weak points if insulation isn’t continuous. Get this wrong and small mistakes quickly become condensation problems.

3. Tackling pipes in a basement

Cold water pipes running through a basement are very prone to condensation when warm air meets the cooler pipe surface. Over time this moisture will soak into plasterboard, timber or insulation, becoming a surprisingly persistent damp problem. Basements are often used to house heating equipment, so insulating these pipes and the room properly helps prevent both heat loss and reduces condensation risk.

4. Insulating suspended timber floors

In older houses where a suspended timber floor sits above a cellar, insulation might be needed around the perimeter of the floor joists. Mineral wool or rigid boards can usually be installed here but make sure that the ventilation paths are maintained. Blocking air bricks in an attempt to make the floor warmer can trap moisture, eventually leading to timber decay.

Choosing the right basement insulation materials

Choosing insulation for a basement is about more than simply achieving a good U-value. Below ground, materials are working in a cooler, more humid environment, with a greater risk of moisture so durability matters just as much.

• Rigid PIR boards are commonly used to insulate basements. They offer a high thermal performance for their thickness, with a typical thermal conductivity around 0.022 W/mK. This allows good U-values to be achieved without using excessive thickness, often important in basement conversions where headroom is already limited. In new build basements PIR is commonly installed either as internal wall insulation over cavity drain membranes or within insulated floor build-ups above the slab. The key limitation however is moisture. PIR performs very well when dry but is not designed to sit in damp conditions, so must always sit on the warm side of the waterproofing system.
• Extruded polystyrene – XPS – is often chosen where there is a greater risk of damp. Its thermal conductivity is slightly lower performing than PIR, typically around 0.030 to 0.034 W/mK, but it has a closed-cell structure that absorbs very little water. This insulation board is well suited for basement floors and areas close to drainage channels where occasional moisture may occur. In new build basements it’s sometimes used beneath the slab or externally against retaining walls where its compressive strength and moisture resistance are particularly useful.
• Mineral wool tends to appear in basement projects within framed internal wall systems or suspended timber floors above cellar spaces. Its thermal conductivity is typically around 0.034–0.037 W/mK. Thermally it performs perfectly well, but moisture is its weakness. Once saturated, mineral wool insulation loses much of its insulating performance and can slump. For that reason it’s best kept entirely separate from any damp structural surfaces.
• Natural eco insulation materials such as wood fibre boards are occasionally proposed because they can buffer small amounts of moisture. In above-ground walls that behaviour can be helpful, but basements are a different environment. In my experience these materials can work, but only where the waterproofing strategy is exceptionally reliable and the internal humidity is carefully managed.
• On new build projects, insulated concrete formwork offers another route altogether. Here the EPS insulation typically has a conductivity around 0.032–0.036 W/mK, and forms part of the permanent shuttering for the concrete wall. Thermally this can work very well because the insulation is continuous, but junctions shouldn’t be overlooked. Where the wall meets the slab, stair structures or upper floors, maintaining insulation continuity is what prevents cold bridges forming later on.

Shop basement insulation

Insulating a basement is all about getting the detail right. Below ground, careful detailing isn’t optional, It’s what separates a cold, damp cellar from a genuinely valuable part of the home. Basements are systems, so insulation products must work alongside the waterproofing and ventilation systems rather than against them.

By using the most appropriate insulation products in the right place, a well-insulated basement stops feeling like a compromise and starts to feel just like any other room in the house – warm, comfortable and free from the musty chill that older cellars are known for.

Warm, sheltered and undisturbed, the insulation in your home makes the perfect nesting spot for pests such as mice, rats, and wasps – none of which you'd particularly want in your loft.

Not only can these pesky creatures cause damage to your insulation, decreasing its effectiveness, but they may also leave droppings and urine behind, which can pose a serious health risk.

To find out the best ways to prevent them from settling in your insulation – and how these tiny creatures get there to begin with – I spoke with three pest control experts to hear their advice.

How do you stop pests in insulation?

 1. Block the entry points

The best way to stop pests from nesting in your insulation is by blocking off access points. To do so, Daniel Steward, Managing Director at Shield Pest Control, recommends inspecting for gaps around fascia and soffit boards, vents, pipe entry points and cable holes – all of which are common routes into insulated areas.

"Any damage to roofing materials should be repaired promptly and vents can be covered with fine mesh to prevent entry while still allowing airflow," he adds.

2. Moisture control

As well as blocking entry points, Daniel also advises keeping moisture levels low in your home by fixing leaks promptly, reducing condensation, and maintaining good ventilation – a damp loft is a golden opportunity in the eyes of a pest.

You can solve most of these problems by ensuring your home is fitted with extractor fans in wet rooms and investing in one of the best dehumidifiers (though this won't be suitable for use inside an unconverted loft). You can check your home's humidity levels using a hygrometer.

3. Keep your loft space tidy

By keeping your loft space clean, tidy, and free from clutter, you'll reduce the chances of rodents (such as mice) settling in, as they will have fewer sheltered spots to choose from, explains Daniel.

4. Remove food sources

One of the fastest ways to attract pests into your home is by leaving out potential food sources. Things like leaving wood waste outside your property and using loose lids on your bins are big no-nos and are likely to attract a long list of unwanted creatures.

The same applies to your garden, too. You should avoid leaving bird seed too close to your property or having overhanging branches close to your roofline, warns Daniel.

5. Watch for early signs

Watch out for warning signs such as scratching and scurrying noises, droppings, chewed wiring and nesting material, all of which could point to an infestation in your insulation. The sooner you find out and can take action, the better.

"If pests have already entered the insulation, acting quickly is important, as contaminated insulation may need to be professionally removed and replaced to fully resolve the issue and prevent further spread within the property," says Daniel.

"In these cases, it’s always advisable to contact a professional pest control company and we can assess the situation, safely remove the infestation and recommend proofing measures to help prevent further damage to the home."

What causes pests in insulation?

We now know how to prevent pests in our insulation, but what actually causes them?

"Pests are attracted to any place that provides shelter and a food source, and will climb pipes, wiring, trees etc. to find an entry point – particularly in insulated lofts," says Darren Backhouse, Partner at MJ Backhouse Pest Control.

"We’ve seen this happen before through roof damage or gaps in a property exterior that let mice, rats or even squirrels in. We’ve also dealt with rats in cavity walls where they used the insulation for nesting."

Tony King, pest control expert at The Pied Piper, adds that the quiet, dark and undisturbed nature of a loft makes it the perfect place for pests to breed and raise their young. Homes with small entry points near the roofline, vents, or soffits offer easy access.

What are the signs of pests in insulation?

According to Daniel Steward, these are the the main signs of a pest infestation such as squirrels in the attic:

1. You can hear scratching or scurrying noises
2. You can see droppings and urine
3. You notice chewed wiring and nesting material

To recap, the easiest way to prevent pests in your insulation is by blocking the access points and making it as unhabitable as possible.

For more pest control advice, read our guide on how to deter wasps and how to get rid of rats in your home.

Homeowners across England are facing difficulties with spray foam insulation installed in their roofs, with some struggling to sell or remortgage properties as a result.

The insulation, installed as part of the government-funded Green Homes Improvement Scheme (GBIS) and ECO4 energy-efficiency schemes, can be safe when correctly fitted, but faulty installations can cause serious problems.

The government has confirmed that it will not provide direct financial assistance for removal, leaving homeowners to rely on installers, guarantees or dispute resolution schemes.

Problems with spray foam insulation

Spray foam insulation is designed to improve a home’s energy efficiency by sealing gaps and reducing heat loss. However, when installed incorrectly, it can trap moisture, cause condensation, and lead to timber decay in roof structures.

These issues have created mortgage and resale problems, with research from the HomeOwners Alliance showing only 25% of mortgage lenders and no equity release providers willing to lend on affected properties.

Costs for removal can also be high – Checkatrade estimates around £3,200 for a typical three-bedroom detached house.

It is important to note that not all spray foam is problematic. Properly installed insulation, following professional standards and product certifications, generally does not pose these risks. The issues primarily arise from faulty or non-compliant installations.

Government schemes and official guidance

The spray foam insulation in question was often installed through GBIS and ECO4, which were government-backed schemes providing financial support for energy-efficiency upgrades.

According to the UK government website, consumers affected by faulty installations are entitled to remediation by the original installer or via an insurance-backed guarantee, but the government will not provide direct financial assistance for removal.

Previous guidance also stresses that homeowners should:

• Keep paperwork from their installation, including test certificates from bodies like the British Board of Agrément (BBA).
• Consult accredited surveyors and professionals to assess whether remedial action is necessary.

This approach aims to ensure that homeowners receive fixes through responsible parties rather than taxpayer-funded programs.

Government response to our enquiry

In a response to an enquiry, officials clarified: “Only a small number of households had spray foam installed through ECO or GBIS. Any household with any measure fitted under GBIS or ECO schemes is entitled to remediation for any non-compliant work (including any spray foam) through the original installer."

They continued: "All measures must have a guarantee, although the length of these guarantees varies by measure and policy. Consumers are encouraged to use certification bodies and TrustMark existing complaints processes, should they need to.”

In other words, the government will not pay for removal, but homeowners with faulty spray foam can pursue remediation via the installer or their insurance-backed guarantee.

Consumer groups, however, say more needs to be done to address the financial impact on homeowners. Paula Higgins, Chief Executive of the HomeOwners Alliance, said: “The ECO4 grant and Great British Insulation Scheme (GBIS) both fund the installation of spray foam to eligible households. It can’t be that homeowners convinced to install spray foam at a significant personal financial cost, and in many cases with help of government grants, are now faced with bills for hundreds if not thousands of pounds to remove the product – far exceeding the original installation costs.”

She added that the government also needs to act on rogue removal firms targeting vulnerable homeowners: “We also call on the government’s assistance to stamp out the rogue spray foam removal companies who are scaring homeowners to remove the insulation and are causing even further damage to their homes.”

For now, homeowners with problematic spray foam face costly removals, difficulties remortgaging, potential condensation issues, and no direct government funding – even though the installations were encouraged through government schemes.

Nationwide is expanding its Green Additional Borrowing offer, letting homeowners borrow up to £20,000 interest-free for eco-friendly home improvements.

The scheme is available for existing mortgage customers and includes upgrades like solar panels, insulation, and energy-efficient windows.

Following a successful first round in 2024, demand is high, and homeowners looking to create their own eco homes are urged to apply quickly before availability runs out.

0% loans: How do they work?

The Green Additional Borrowing mortgage allows existing Nationwide mortgage holders to borrow between £5,000 and £20,000 at 0% interest for either two or five year terms.

The loan must be used exclusively for energy-saving improvements, such as boiler upgrades, solar panels, air-source heat pumps, loft or cavity wall insulation, double or triple glazing, and electric car charging points. Monthly payments remain interest-free for the chosen term, after which the remaining balance converts to Nationwide’s standard mortgage rate.

Henry Jordan, Nationwide’s Group Director of Mortgages, said: “We are committed to helping our members improve the energy efficiency of their homes. Extending our zero per cent Green Additional Borrowing products will help another five thousand households who want to retrofit their home and can afford long-term investment but struggle to meet the upfront costs.”

This is an expansion of the 2024 offer, which proved extremely popular. That scheme, also allowing up to £20,000 for green home upgrades, saw its first allocation sell out quickly, demonstrating the appetite for affordable, eco-friendly home improvements.

Who qualifies for Nationwide's 0% loans?

To access the Green Additional Borrowing, homeowners must have an active Nationwide mortgage, with the combined total of their existing mortgage and the additional borrowing not exceeding 90% of the property’s value.

The additional borrowing term cannot exceed the remaining term of the existing mortgage, and only one Green Additional Borrowing mortgage per property is allowed.

Nationwide recommends that interested homeowners act quickly, as the previous round in 2024 sold out fast due to high demand for energy-efficient upgrades.

Why it matters for homeowners

With energy costs rising and climate concerns increasing, the mortgage gives homeowners a practical way to make their homes more energy-efficient without upfront costs.

Home improvements financed through this scheme can reduce energy bills, increase property value, and contribute to the UK’s decarbonisation goals.

By doubling the availability from the initial 2024 offer, Nationwide is making it easier for thousands more households to access interest-free funding for green upgrades, but limited availability means acting quickly is essential.

A new report has delivered a stark verdict on the government’s flagship home insulation schemes, calling the collapse of the ECO4 and Great British Insulation Scheme a “wake‑up call” for retrofit policy.

It says past programmes focused too narrowly on emissions targets while failing to fix basic home repair issues, leaving many households cold, damp and with rising bills.

The authors argue that without major changes, future retrofit programmes risk repeating the same mistakes and continuing to miss the homes that need help most.

Damning findings from Government schemes

The report – released this week by the Centre for Housing and Place – paints a critical picture of the Energy Company Obligation 4 (ECO4) and the Great British Insulation Scheme, both of which were terminated after widespread problems and poor outcomes.

According to the report, these schemes often failed to address fundamental repair needs before installing energy efficiency measures, leading in many cases to damp, mould and other issues that undermined the intended benefits. The report called the delivery model “inadequate” and says the heavy reliance on private contractors incentivised cutting corners rather than quality work.

Researchers also note that while both programmes aimed to reduce carbon emissions and help households cut energy costs, too many homes, particularly in older and underserved communities, were excluded because they required more complex repair work before retrofit.

With rising energy bills continuing to affect millions of families, the report warns that this gap has left too many vulnerable households behind.

Calls for a new framework

In place of the old schemes, the report suggests a radical shift toward area‑based and neighbourhood‑level programmes that tackle both energy efficiency and basic home repairs together.

Rather than focusing solely on heat pumps, insulation or solar panels, the authors argue that retrofit policy must be grounded in ensuring all homes reach a basic standard of health and safety first.

This approach, they say, would deliver bigger, long‑lasting benefits in terms of lower bills, healthier homes and reduced greenhouse gas emissions.

Importantly, the report emphasises that lessons from the recently scrapped ECO4 scheme and its predecessors must inform future policy design. It calls for new institutional frameworks, stronger oversight, better community engagement, and a move away from short‑term contractor models toward sustained investment in skills and quality delivery.

Learning from past errors

The report doesn’t just criticise past programmes – it lays out a practical roadmap for getting retrofit right the next time, for instance, with the government's new Warm Homes Plan.

Instead of repeating the same narrowly focused initiatives, it calls for a fundamentally different way of delivering home improvements that ensures quality, fairness, and impact.

The four main suggestions from the framework proposal are:

1. Plan at neighbourhood level, not project by project

Rather than funding individual measures house by house, retrofit should be organised at the scale of whole streets or areas.

This allows planners to prioritise homes that need structural repairs first (e.g., damp proofing, roof fixes) before energy upgrades – something that past schemes often ignored. The report argues this is essential for both effectiveness and cost‑efficiency.

“You can’t just bolt insulation onto a broken house – first you have to fix the house,” said one lead author. “Neighbourhood‑scale planning stops energy upgrades becoming expensive window dressing.”

2. Build quality into the system from the start

A major shortcoming of programmes like ECO4 and the Great British Insulation Scheme, the report says, was the reliance on short‑term contracts and minimum cost incentives that encouraged rushed or substandard work.

To fix this, it proposes:

• Strong independent quality checks at every stage, not just after installation
• Clear workmanship standards tied to funding
• Public‑sector or long‑term community retrofit teams that develop expertise rather than shifting hundreds of contractors in and out

“Quality assurance can’t be an afterthought or box‑ticking exercise,” the report states. “Homes must be retrofit‑ready before energy measures are installed."

3. Protect residents, especially tenants

Too often, the people living in homes did not see the benefits of retrofit because costs were passed on through higher rents or disruption forced temporary (and sometimes permanent) displacement.

The report recommends:

• Tenant safeguards so landlords cannot raise rents or evict tenants because of retrofit works
• Compensation or accommodation support during disruptive works
• Stronger enforcement of housing standards alongside retrofit funding

“Investment in homes should improve lives - not lead to eviction and higher rents,” a senior researcher said.

4. Stop scaling up failed models and start building capacity

The authors make clear that simply spending more money on the same delivery models will not solve deep‑rooted problems. Instead, they call for public investment in:

• Dedicated retrofit bodies at county or regional level
• A skilled, permanent retrofit workforce
• Integrated planning between energy, housing and health agencies

“Expanding yesterday’s schemes just expands yesterday’s mistakes,” the report warns.

“We need new institutions, not bigger versions of broken ones.”

The Government’s newly unveiled £15 billion Warm Homes Plan risks becoming a "costly mistake" by prioritising high-tech heat pumps over basic insulation.

The Builders Merchant Federation (BMF) say that removing mandatory insulation requirements from the Boiler Upgrade Scheme allows homeowners to install expensive low-carbon heating into "leaky" properties that cannot retain the warmth.

Without a "fabric first" approach, they warn thousands of homeowners could be left with underperforming systems and unexpectedly high energy bills.

The insulation omission

While the Government has pledged nearly £15 billion to upgrade five million homes, the BMF has voiced serious concerns regarding a lack of focus on the building's "fabric."

Since May 2024, Ofgem has removed the requirement for loft or cavity wall insulation to be in place before a homeowner can claim a £7,500 Boiler Upgrade Scheme grant.

BMF CEO John Newcomb argues that the current strategy is fundamentally flawed, stating: “It seems illogical that a £7,500 Boiler Upgrade Scheme grant can be claimed without measures to properly insulate homes first.”

For renovators, this policy shift creates a risk of installing advanced tech that the home simply isn't ready for.

The 'bath without a plug' warning

The criticism centres on the efficiency of low-carbon technology in poorly insulated spaces. Mike Beard, Chair of the BMF’s Insulation and Dry-Lining Forum, describes the current policy as "like running a bath and not putting the plug in."

Because heat pumps typically operate at lower flow temperatures than traditional gas boilers, they require a well-insulated environment to function effectively.

“It’s imperative that we don’t lose sight of the need for fabric-first, well-insulated properties,” Beard warns, noting that failing to do so will cause the benefits of energy-efficient measures to “backfire” as heat escapes faster than it can be generated.

Calls for a fabric-first future

The BMF is now calling for the Warm Homes Plan to be "re-plumbed" with a fabric-first strategy.

CEO John Newcomb argues that while the £15 billion allocation is a welcome "long-overdue" investment, the logic of subsidising £7,500 for a heat pump without ensuring the home can hold that heat is "illogical."

The federation is urging the Government to reintroduce measures that ensure insulation is installed professionally and prioritised as the foundation of any home renovation to ensure the UK’s housing stock is truly fit for a net-zero future.

Thousands of UK homes upgraded under government insulation schemes now face serious defects, damp, and potential safety hazards, leaving families exposed to potentially unaffordable repair bills.

Audits reveal that 98 % of external wall insulation and nearly a third of internal installations were defective, while fewer than 10 % of affected homes had been fixed by late 2025.

Experts warn that systemic oversight failures and underfunded guarantees mean the financial burden could fall on households rather than the state.

'Catastrophic fiasco' leaves homes damaged

A parliamentary audit reveals that homes upgraded under ECO4 and the Great British Insulation Scheme launched to cut bills and improve energy efficiency – instead face widespread substandard work and ongoing costs.

Sir Geoffrey Clifton‑Brown, Chair of the Public Accounts Committee (PAC), called the result of the scheme “the most catastrophic fiasco” he has seen in his 12 years on the committee.

He said: “Potentially thousands of people are now living with health and safety risks in their homes, and we have nowhere near enough assurance that they are not financially exposed to unaffordable bills to repair defective works.”

The National Audit Office found that in inspections up to mid‑January 2025, 98 % of external wall insulation and 29 % of internal installations were defective, creating health risks and structural problems for households.

Fraud fears compound the crisis

The PAC report highlights systemic weaknesses that no single organisation had responsibility for preventing fraud or poor quality.

Ofgem has flagged installations worth 1.75 % of scheme value as fraudulent, but MPs suspect the true figure is much higher due to non‑compliance and weak monitoring.

Sir Geoffrey Clifton‑Brown said: “The levels of non‑compliance found here are so high that this matter should be referred to the Serious Fraud Office.”

TrustMark, the government‑endorsed quality scheme, has been criticised for failing to identify risks early, auditing less than 10 % of affected homes by September 2025. This leaves households uncertain if their properties will ever be properly fixed.

Households face bills beyond guarantees

Original installers are meant to fix defects, with guarantee providers covering costs up to £20,000, but some cases reportedly exceed this, leaving households potentially liable.

Campaigners warn that families who thought they were signing up for lower bills and warmer homes now risk extensive repairs and health hazards.

Jess Ralston, Head of Energy at the Energy & Climate Intelligence Unit (ECIU), offered broader context in response to ongoing policy discussions this week, saying: "This report shows that people’s homes and lives have been damaged by these faulty installations… There has clearly been a lack of proper regulation going back many years, but this government now has an opportunity to bring in proper standards in the Warm Homes Plan.”

Government ministers state that no household should have to pay to fix defects, but the PAC report warns there is no credible, funded plan yet to guarantee this outcome.

Cavity wall insulation is one of those home improvements that sounds like a no-brainer, promising a warmer home, fewer draughts and lower energy bills . In most cases, that’s exactly what you get, provided your home is actually suitable for it and the job is done properly.

Unfortunately, many homeowners jump in too quickly, tempted by government grants or persuasive sales pitches, and end up with problems. Damp patches, crumbling plaster and not achieving the promised energy savings are all possibilities.

This article sets out the most common cavity wall insulation mistakes and, more importantly, explains how to avoid botching when adding this type of home insulation.

1. Not checking if your home is suitable

The first and biggest mistake is assuming that cavity wall insulation is right for every home. It isn’t. Some properties just aren’t designed for it, and installing cavity wall insulation in the wrong type of wall can cause serious problems.

Older houses might have smaller cavities within the walls which can’t be properly filled with insulation. If the brickwork is particularly porous, or if the walls are regularly exposed to driving rain, then this could make cavity wall insulation an unsuitable choice. Timber frame properties are another big red flag. Their walls rely on ventilated cavities to keep the timber dry. Filling this space with insulation can trap moisture, leading to rot, structural problems and difficulties with securing insurance cover and mortgages.

Before carrying out cavity wall insulation, always have a professional survey. A proper inspection will identify the cavity width, check for any existing damp, and assess the general condition of the external walls. A reputable installer will insist on this as they won’t want long terms defects just as much as you.

2. Choosing the wrong insulation material

Even if your home is suitable, choosing the wrong insulation material can result in unexpected problems. The right type of insulation will depend on how your home is construction and also how exposed it is to severe weather conditions.

Mineral wool insulation is one of the most common options. It’s breathable and a good insulator, but it can absorb water if moisture gets into the cavity. Polystyrene beads are another popular choice and are water-resistant and able to fill awkward spaces easily. Polyurethane foam, expands to fill the cavity completely but has greater risk of defects particularly if the cavity isn’t constructed correctly.

Homeowners often go with whatever product the installer recommends without questioning its suitability. If the installer has limited product options or isn’t technically competent the wrong insulation product could be proposed. For example, recommending mineral wool or eco insulation in a wall with cracks or weak pointing that allows moisture to enter the cavity. If your home faces frequent wind-driven rain or you live in a coastal area, the installer should take that into account and recommend that repairs are undertaken.

It’s always best to ask why a particular material is being proposed and how it’s expected to perform. A good installer will be happy to explain all the options and provide a comparison of the features and benefits they offer. A bit of research before signing off will save a load of problems and hassle later.

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3. Poor installation techniques

Even the best insulation can fail miserably if it’s not installed properly. A common mistake is incomplete filling of the cavity. If the insulation doesn’t reach every part, voids will form, creating cold patches that allow heat to escape. These cold spots attract condensation and eventually mould will form.

Blocked vents are another common issue. Air bricks and ventilation openings should never be blocked as part of an installation. Blocked vents reduces airflow, increases condensation risk, leading to mould and damp problems.

Incorrect drilling patterns are also surprisingly common. Installers should follow a precise layout of drill holes across the external walls to ensure the insulation is evenly distributed. Drilling insufficient injection holes results in uneven insulation filling and if the holes aren’t properly sealed afterwards, rainwater can seep in leading to damp.

Good installers will use thermal imaging cameras and borescopes to checks and confirm that the cavity has been completely filled. If your installer doesn’t offer this, then ask questions quickly.

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4. Ignoring existing damp issues

It sounds obvious, but if you already have damp problems don’t install cavity wall insulation until the problem has been fixed. Despite what promotional literature might say, insulation isn’t a magic cure and poor installation can make things worse. Once insulation is in place, moisture that would have evaporated in an adequately ventilated cavity can become trapped. If there’s rising damp, penetrating damp, or even leaks from damaged guttering, these must be fixed well ahead of cavity wall installation taking place.

Installers sometimes downplay the importance of preparation works as this makes jobs more expensive and longer to complete. A good building survey should identify any damp issues and make recommendations for carrying out repairs. It’s far better to wait a few weeks for these to be done, rather than rushing and having to deal with saturated insulation and mould growth.

5. Lack of proper ventilation

Cavity wall insulation will make a home warmer and more airtight, which can be a double-edged sword. Older homes tend to rely on natural ventilation through air leaky walls to keep them well-ventilated and dry.

If this ventilation isn’t maintained, the result can be condensation on cold surfaces, particularly in areas with high humidity such as bathrooms and kitchens. Maintaining good ventilation is essential so check that air bricks that bridge the cavity aren’t blocked by the insulation. Also make sure that extractor fans are working correctly, trickle vents on windows are open, and loft spaces with insulation have adequate eaves ventilation.

6. Not using a certified or competent installer

There’s no shortage of stories about poor workmanship in the insulation industry. Some homeowners are lured in by cheap deals for insulation costs or slick sales pitches promising hassle free installations and significant savings on energy bills.

Using an unqualified or uncertified installer can lead to disastrous results. Without the necessary technical know-how, installations might not meet industry standards and resolving problems later, can become a complete nightmare.

Look for installers who are registered with recognised bodies such as CIGA (Cavity Insulation Guarantee Association), TrustMark or work with reputable organisations such as RetrofitWorks. Member installers are often required to be signed up to recognised industry schemes, have to follow specific standards and provide guarantees for their work.

Whilst cavity wall insulation might seem straightforward, DIY installations are best avoided. Doing the job correctly requires specialist equipment and training and the risk of causing damage far outweighs any savings from trying to do it yourself.

7. Failing to maintain and inspect

Once cavity wall insulation is installed, it’s completely out of sight and out of mind. Most people forget about it completely, but like any part of a house, it needs a little maintenance to keep it performing well and as intended.

Over time, insulation can settle, become damp, or degrade if it’s exposed to water. Cracked render, leaking downpipes, or deteriorating mastic pointing or mortar joints can allow rainwater to enter the cavity, soaking the insulation and reducing its effectiveness.

It’s a good idea to inspect exterior walls at least once a year. Look for cracks, damaged pointing, or anything that might allow moisture to get through to the cavity. If you notice cold spots or damp patches, have a professional carryout an inspection to find out why.

Remember, early intervention will stop minor issues turning into a major headaches. Simple maintenance tasks, such as cleaning gutters or repairing leaking downpipes will keep water under control and avoid damage to the cavity wall insulation.

8. Over-insulating or under-insulating

It’s possible to get insulation wrong even when it’s installed correctly. Too little, and you’ll not realise the planned energy savings. Too much could create other problems.

The more common mistake is under-insulating, usually because the installation wasn’t properly carried out. That leads to patchy performance, with some areas of the wall staying cold whilst others are warm.

Over-insulating isn’t usually a problem, but adding large amounts of insulation without a proper design can trap moisture between the insulation and wall layers, which again risks damp and further problems

The key is design and compliance with manufacturers installation recommendations. Firstly, the correct insulation product should be used to suit the cavity size and wall type. Assessments should support the design proposal such as U value calculations and condensation risk analysis. A competent installer will complete these in advance of an installation to ensure optimal thermal performance is achieved without compromising the building’s ability to breathe and dissipate moisture.

Cavity wall insulation can make a huge difference to a home’s comfort and energy efficiency, but only if it’s done right. The biggest issues tend to come from skipping surveys, using the wrong materials, or cutting corners on when installation is carried out. Mistake might at first seem small but the impact of getting things wrong can be expensive.

If you’re considering cavity wall insulation, my advice is to take your time, do your research and undertake it properly to make sure it lasts. You can read more on how to insulate a house as well as how long does insulation last in my in-depth pieces on the topics.

Have a professional survey carried out, check installer’s credentials, verify that the materials will be properly handling and installed. Once the installation is complete, keep an eye on how it performs and carry out simple maintenance to prevent problems developing.

The Warm Homes Plan, first promised in May 2024 by Energy Secretary Ed Miliband, was designed to tackle rising energy bills and reduce carbon emissions by upgrading the energy efficiency of millions of homes.

The plan, which aims to support insulation, low-carbon heating, ventilation, and solar technologies, was expected to provide clarity and funding for households across the UK.

Officials have now confirmed the full plan will not be released until January 2026, leaving homeowners and advisors uncertain about what support will be available and when.

What the Warm Homes Plan includes

The plan is intended to upgrade up to 5 million homes over the next five years, helping households cut energy costs while contributing to the UK’s climate targets.

Key programs, such as the £7,500 Boiler Upgrade Scheme for heat pumps, may continue, but full details on eligibility, grant levels, and low-interest financing are still unknown.

So far, the government has confirmed £1.29bn for social landlords and £500m for local authorities to fund energy efficiency upgrades, but individual homeowners still have no clarity on what support, grants, or loans will be available for their properties.

Reasons for the delay

Officials say the delay is due in part to the need to finalise a replacement for the scrapped Energy Company Obligation (ECO4) scheme, which was ended in the Autumn Budget.

Combined with £1.5 billion in cuts to household energy programs, the government says it is taking extra time to ensure the plan provides “clear support for homeowners while safeguarding thousands of clean energy jobs.”

A DESNZ spokesperson said the government is “doubling down on support for home upgrades” and will outline plans to help households and support jobs “soon.”

Impact on homeowners and industry

The delay has left homeowners and the retrofit sector in limbo.

Becky Lane, CEO of Birmingham-based retrofit company Furbnow, which has upgraded more than 1,000 homes across England and Wales, said: “After slashing ECO and £1.5bn in the Autumn Budget, the industry desperately needs certainty. The Warm Homes Plan is now over eight months late. We want to invest and grow, but it’s impossible when government keeps announcing cuts while withholding the policy we need to deliver.”

She added: “Eight months of delays and counting. Companies like ours are ready to scale up and deliver better outcomes for homeowners, but we can’t plan or invest without knowing the rules of the game. The government promised the Warm Homes Plan in May. It’s now December, ECO has been scrapped, and we still have no clarity on what replaces it. Set a date and stick to it. This sector can’t operate in limbo.”

Lane also highlighted the importance of targeted low-interest finance, saying loans must focus on upgrades that need the most support, insulation, heating systems, and ventilation, rather than narrowly on solar and batteries.

Without clear guidance, millions of homeowners are left uncertain about when or how they can improve their homes.

While adding loft insulation is certainly one way to improve your home's energy efficiency, making loft insulation mistakes can result in your hard work backfiring and leading to more problems than you even started with.

However, follow the correct advice on how to insulate a loft and there's no doubt you and your home will reap the rewards.

With building and roofing experts to hand, we're here to explain the most common loft insulation mistakes homeowners make so you can avoid a future that sees you ripping out your hard work and starting over again.

Mistake one: lack of ventilation

If you weren't aware there is such a thing as too much insulation, you may be heading towards making one of the most common loft insulation mistakes – over filling your loft with insulation that can lead to a lack of essential ventilation.

"It's very common for homeowners to insulate their lofts right up the edges or eaves of a roof, as the common perception is that if they don't, cold air will enter into the loft space and this needs to be avoided at all costs," says Mike Storey, roofing expert at UK Flat Roofing & Insulation.

"However, this isn't entirely true, says Mike. "Loft ventilation gaps are essential as they allow allow any moisture build-up to dissipate. The most common insulation material used in a loft is loft roll, and as soon as this get damp or wet its thermal value is ruined, meaning its performance is reduced significantly," he warns.

“If you block eaves vents or air bricks in lofts then this will only lead to problems,” confirms building expert, Mark Stevenson. “Your once dry loft will soon become a haven for damp and mould.”

The solution? “Make sure you have ventilation paths when insulating your loft," advises Mark. "This means using cross flow vent trays that are fitted between the rafters at the eaves, letting air continue to flow throughout the space.”

Mistake two: Poor installation

If, as part of your loft improvement measures you're considering boarding your loft in order to create loft storage space, this next mistake is one you need to bear in mind.

Although maximising on storage space may be the goal, this doesn't mean you can cram your loft insulation below the boards and hope for the best.

"A common loft insulation mistake we see us homeowners putting the loft roll into the joist space and then boarding directly over it," confirms Mike Storey.

"This will squash or compress the insulation, and as loft roll uses the air trapped between the glass fibre strands to work, compressing it to a thickness less than it's designed to be, stops it from working correctly," warns Mike.

The required amount for loft insulation in accordance with Part L of the building regulations will depend on whether you are building a new self build or refurbishing an existing property.

However, when renovating a house, you'll likely find that the maths doesn't quite work out – making this particular loft insulation mistake an easy one to make.

"Standard joists are commonly only 150mm - 200mm deep in most roofs, meaning the insulation is automatically higher," explains Mike. "Your best solution is always to use a product such as Loft Legs to increase the space before adding boards on top of the legs.

"Always add 50mm of ventilation gap above the insulation and below the timber floor that is connected to the eaves on both sides," advises Mike, "or you will end up with damp issues caused by loft condensation."

Mistake three: Gaps in the wrong places

Although the argument for leaving gaps to allow for airflow still stands when installing loft insulation, it's not always the case when using the warm roof method for insulating your loft. This is when the roof is insulated – most commonly with insulation boards – rather than insulating at floor level between the joists.

"Even the tiniest of gaps can lead to problems in this instance," confirms Mark Stevenson. "Gaps can result in cold spots, loss of heat and potentially issues again with mould and condensation."

"The correct way to insulate at this level is to ensure you have ventilation above and below, and a breather membrane installed," advises Mike Storey. "Then, always ensure the boards are taped up along the joints and at the edges. Also make sure that any damage to the foil on the board is taped, as otherwise this will compromise your vapour barrier layer.

"If it's a multifoil system ensure that they are taped up between each roll and around the edges," he adds. "This prevents moisture getting into the roof. You will still need ventilation at the eaves, above the insulation in order to prevent any moisture build up, but making sure it's neatly fitted is essential."

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Mistake four: Using the wrong insulation or method

Choosing the right type of insulation, and how and where to install it is the best way to avoid making loft insulation mistakes in general, but how do you know?

If you're embarking on a loft conversion, you'll need to consider insulating at roof and floor level to make the space habitable. But what if it's just for storage?

"Start by checking if the items in the loft need to be stored at room temperature, or if they can fluctuate between being hot in summer and cold in winter," suggests Mike Storey. Fully insulating the space will give you maximum insulation, but this may not be necessary.

Using the right product is also key, warns Mark Stevenson. "Too often people rush to insulate without understanding that there isn't a one-size-fits-all approach. Spray foam insulation used in between roof rafters is a prime example. This can lead to rotting timbers and expensive repairs.

"If you aren't sure what product is best for your loft, make sure you consult with an expert first in order to pick the best solution," he advises.

If after reading this you think it might be time for an upgrade, make sure you follow our guide to removing loft insulation safely, and work out your budget with our guide to loft replacement costs.

And finally, if you've suddenly realised there's an unwanted gap in the form of a 'bare' loft hatch, take the time to insulate your loft hatch too.

If there’s one part of a self build or renovation that’s easy to underestimate, it’s insulation. Most of us know it’s essential for keeping the house warm and reducing energy bills, but the reality is that insulation isn’t just about stuffing some material into walls or roofs and calling it a day.

Done wrongly, it can lead to damp, drafts, mould, and a home that’s far less comfortable than it should be.

Over the years, I’ve seen plenty of errors – the kind that quietly undo all the hard work and expense of insulating in the first place. If you’re planning an upgrade or new build, here are the most common insulation mistakes and how to avoid them.

1. Not checking if your home is suitable

Before any type of insulation is installed, its vital that it’s checked for suitability. Too often, self builders rush in and start insulating without checking if the application (cavity walls, timber frames, solid masonry walls etc) can be insulated. For example, using cavity wall insulation on a timber frame building, or spraying foam between the rafters of a roof space.

Without proper ventilation, moisture can get trapped causing rot, and insulation that gets wet or suffers thermal bypass will perform far below expectations, wasting money rather than saving it.

The solution is to always start with a professional advice. This might be a survey or an energy assessment from a qualified surveyor or designer who’ll assess the building, spot potential problems (like damp or poor ventilation), and recommend the best materials and insulation methods.

2. Choosing the wrong type of insulation

Insulation isn’t a one-size-fits-all product. Different parts of a house, such as the loft, walls, floors, or roof, will require different approaches and usually a different insulation product.

For example, fibreglass is great for dry lofts but not suitable for damp spaces. Rigid insulation boards are really effective under floors and in walls, but they’re less suitable if they need to fit awkward shapes or uneven surfaces. An obvious alternative is spray foam insulation and whilst this might look attractive, if its installed incorrectly, it can cause major problems

Most self builders will look for a product that’s very thermally efficient, but it’s also important to consider moisture resistance, fire safety, and breathability as well. Again it might be best to consult a professional who’ll understand the product and will be able to compare it with other alternatives.

Alternatively, take time to do your own research, look at the best ways to insulate a home, and read the manufacturers literature and technical information such as installation instructions and declarations of performance (DOP’s).

3. Poor installation — gaps and voids

Even the best insulation product won’t perform properly if its not installed properly. Gaps, overlaps, or over compression of quilts will affect an insulation material's actual performance. Neatly insulated lofts will be compromised by something as simple as tiny gaps, resulting in cold spots and heat loss, higher bills and potentially condensation and mould.

It’s important to pay attention to detail. Insulation should fit snugly, without being squashed or stretched. Cavities should be consistent and well-ventilated and rigid insulation materials must be cut precisely around timbers and joists.

Achieving a good job requires care, so measure twice, cut once. To help get things right, invest in innovative products such as compressible gap fillers including Compriband or Gapotape, available from Insulation Online, which will fill gaps and prevent air movement and thermal bypass.

4. Neglecting airtightness

Insulation works by slowing the transfer of heat from a warm to a cold space. But insulation on its own doesn’t stop air movement. If there are gaps around windows, floorboards, or service penetrations, heat will still escape and cold air will find its way in.

As well as installing the correct insulation product, it’s essential that airtightness is also dealt with. This means installing airtight membranes and vapours control layers along with airtight tapes and sealants to close gaps. A simple smoke test with an air pressure test will check that an installation meets the appropriate level of airtightness, and will help identify where leaks are happening so they can be sealed properly.

Try these products for insulating around windows and doors

5. Blocking ventilation paths

A common misconception is that sealing up every possible gap will make a home more energy efficient. Whilst there is some truth to this, some airflow is essential for adequate ventilation – particularly in lofts and cavities. Blocking eaves vents or air bricks prevents moisture escaping and can quickly turn a dry, healthy space into a damp, mouldy mess.

The solution is simply to maintain ventilation paths when installing insulation. With loft ventilation, cross flow vent trays fitted between the rafters at the eaves will keep air moving. For cavity wall insulation, make sure any air bricks or weep holes are not obstructed when the insulation is pumped in. A good installer will check these things both before and after an installation.

6. Ignoring existing moisture problems

Insulation and moisture typically don’t mix. If there’s an underlying damp problem, insulating over it is like painting over rust – it hides the issue but doesn’t fix it. Moisture trapped behind insulation can be even worse, causing damage to the insulation, structural members and encouraging different types of mould to grow. Once again moisture will also cause the insulation to lose its effectiveness.

The key here is to always carry out a survey and address any damp issues first. Fix leaks, improve drainage, and maintain ventilation. Once the area is dry and sound, the insulation can be installed with confidence. In moisture-prone areas like basements or ground floors, opt for specialist closed-cell insulation products designed for wet conditions. These materials won’t absorb water and will not deteriorate over time.

7. Over-insulating without proper planning

Adding layer upon layer of insulation might sound like a good idea, but can easily backfire. Beyond a certain point, extra insulation provides very little additional benefit, meaning it's important to understand how much is too much insulation. Get it wrong and it can actually create problems by restricting ventilation paths, trapping heat and in some circumstances, becoming a fire risk.

The best approach is to seek expert advice and discuss how a building element should be insulated before making alterations. A good professional will know the best option and when old, tired insulation should be removed. They’ll recommended appropriate products with thermal resistances to such the location and climatic conditions. The objective should be to achieve the right balance of insulation, ventilation, and airtightness so it properly works together. If the building becomes overly airtight, consider mechanical ventilation with heat recovery (MVHR) to maintain healthy air circulation and retain heat.

8. DIY disasters and uncertified installers

Installing insulation might look straightforward, but there’s actually much more to it than meets the eye. DIY efforts can easily go wrong – from leaving gaps and overly compressing quilts, to using the wrong type of material.

Hiring someone who isn’t properly certified or competent can also lead to problems such as wrongly installing spray foam insulation causing structural damage and resulting in insurance and saleability issues. Poor workmanship wastes money, reduces performance, and in some cases, requires costly remediation. In extreme cases properties can even become unmortgageable.

Always seek professional advice and hire qualified, experienced contractors. Look for certifications from reputable bodies such as the National Insulation Association (NIA) or TrustMark. Ask for references, check reviews, and don’t be afraid to ask questions about the appropriateness of materials, ventilation strategies, and guarantees. Professional contractors will appreciate the conversation and will be just as interested as you are in safely making improvements to your home.

For more advice on fitting insulation in the right way, take a look at our guide to installing internal wall insulation in a renovation and make sure you've allocated sufficient funds in your budget to your loft insulation costs.

For most self builders, installing insulation is a no-brainer and the corner stone of improving the energy efficiency of a home. It’s one of those investments that seem to tick every box and by wrapping your home in enough insulation, the result should be that you’ll spend less on heating, live more comfortably, and lower your carbon footprint.

Whilst home insulation is an essential energy efficiency upgrade, there’s a growing awareness that more isn’t always better. Sounds counter-intuitive, but go too far, and you can start to create problems – trapped moisture, poor ventilation, and even overheating.

Effectively insulating a home is a tricky balancing act and whilst you’ll want your home to be energy efficient, it will also need to “breathe” and perform well in all seasons. The key to an energy efficient home is to know how much insulation is enough, and at what point adding more starts to become a problem?

Why you need lots of insulation

Insulation works by slowing down the transfer of heat between a warm and cold place. In winter, implementing the best ways to insulate a home means keeping the warmth from escaping, and in summer it means helping to prevent heat from getting in.

A well-insulated home delivers lower energy bills and by reducing the rate of heat loss (through walls, roofs, and floors) a stable indoor temperature can be maintained with far less reliance on heating systems. This means that boilers, heat pumps and air conditioning systems won’t need to work as hard, saving money and reducing wear and tear.

A well-insulated home doesn’t just stay warm – it creates a comfortable environment to live in. Cold patches and draughts are eliminated and living spaces become quieter with better soundproofing. From an environmental point of view, insulation is one of the most effective ways to reduce your carbon footprint – less energy used for heating means fewer emissions, and a lower carbon footprint.

For all these reasons, insulation is rightly a top priority for most self builders. However, a home that relies on a delicate balance between insulation, airtightness, and ventilation is where things can start to go wrong.

Shop for home insulation products

How much is too much insulation?

Adding insulation always seems like a no brainer, but after a certain point, the benefits taper off. In fact, beyond a certain thickness or level of airtightness, insulation can create as many issues as it solves.

1. When it causes problems with moisture management

A big concern when over-insulating is moisture management. Activities such as cooking, showering, drying clothes, and even breathing produce water vapour which in older homes, is carried away through leaks in the building fabric. But in a highly insulated, airtight home this moisture can become trapped.

The problem is that warm, humid air condenses when it comes into contact with cooler surfaces such as the inside of an exterior wall. Over time, this condensation damages the building fabric, creating mildew, damp patches and mould growth. Prolonged damp conditions behind plasterboards and within insulation layers can lead to rot and structural damage and wet insulation materials will lose their thermal resistance and become ineffective.

When building with timber frame or SIPs, moisture management is particularly important and these structures will require careful detailing to prevent interstitial condensation within the walls. Masonry based walls can have problems too and cold bridges can become damp patches, leading to mould growth and unhealthy living environments.

2. When it causes ventilation issues

A common side effect of highly insulated, airtight buildings is poor indoor air quality. Without adequate ventilation, airtight homes have trouble replacing stale air. Humidity levels then rise resulting in respiratory issues and condensation.

Self-builders who’ve gone for a 'sealed box' then find their home feels stale and stuffy which can even lead to what’s known as 'sick building syndrome,' where occupants feel unwell simply from being inside the property.

The answer is to use Mechanical Ventilation Heat Recovery (MVHR) systems to bring in fresh air whilst extracting the stale indoor air and retaining its warmth. These systems work brilliantly when properly specified and installed, and are essential for highly insulated, airtight homes.

3. When the amount of insulation causes overheating in summer

Whilst insulation keeps your home warm in winter, it can also make it too warm in summer. In a highly insulated home, heat enters through windows or from appliances and becomes trapped inside. Without adequate shading and ventilation, the indoor temperature rise quickly and become unbearable. This issue mostly commonly happens with south-facing homes with large areas of glazing.

For self builders aiming for true year-round comfort, the answer lies in balance. It is possible to have a highly insulated home that doesn’t overheat, provided glazing and shading is well designed along with adequate ventilation strategies.

The law of diminishing returns

There’s a law of diminishing returns when it comes to adding insulation. The first 100mm of insulation added to a wall for example, makes a huge difference to energy efficiency. But the benefit delivered by the next 100mm is not nearly as much. By the time you’re doubling or tripling standard insulation levels, the improvement to your home’s performance is minimal compared to insulation cost.

If a wall already achieves a U-value of 0.18 W/m²K (the current building regulations target), adding more insulation might only save you a few pounds in terms of heating costs. If the insulation upgrade costs thousands, the payback could take decades.

For self builders with a limited budget, that extra money might be far better spent elsewhere – better windows, renewable technologies, or mechanical ventilation systems.

Finding the 'optimal' level of insulation

There’s no single answer that fits every project and the right amount of insulation will depend on the location, the architectural design, as well as what you want to achieve.

1. Climate zone considerations

A home in the Scottish Highlands faces very different conditions than one in say Devon. In colder regions, thicker insulation makes perfect sense, but in milder parts of the country, pushing insulation levels too far can result in overheating and unnecessary expense. Furthermore, orientation, window placement, shading, and ventilation will all play a part in how much insulation is actually needed.

2. Regulatory requirements and U-values

The building regulations set out minimum insulation standards and U-values to achieve energy efficiency standards. For most new builds, these targets are around 0.18 W/m²K for internal wall insulation, 0.13 for roofs, and roughly 0.13 – 0.15 for floors.

Whilst it’s fine to go beyond them, there’s a point where the gains flatten out, so it’s not necessarily beneficial to push too far past the standards. And if you want to build, say, a Passivhaus or near-Passivhaus standards, then the insulation strategy will need to be supported by airtightness detailing and mechanical ventilation to maintain indoor air quality.

Getting a professional assessment

If you still want to up-spec the insulation, then the best approach is to get professional advice to understand the implications. An energy assessor uses software such as SAP or PHPP to model a home’s energy performance and predict its EPC rating.

These models simulate heat loss and energy consumption to provide a clear picture of how different insulation levels will perform in a specific context. For self builders, this kind of modelling is invaluable and helps to avoid costly mistakes as well as ensuring a good ROI.

Ultimately, the best-performing homes aren’t the ones with the thickest insulation - they’re the ones where everything works in harmony. Insulation, airtightness, ventilation, and shading, all play their part.

If one is pushed too far without considering the others, the system as a whole can falter. The goal is to create a home that’s comfortable, efficient, and durable and not one that traps heat and moisture in the pursuit of energy savings.

For more advice on insulating your home, find out the areas of your home never to insulate, and if you're looking extending your home rather than self building a new one, following our guide to insulating an extension.

Most of us only deal with home insulation a few times in a lifetime, so many of the materials used to insulate buildings are little known to the average person.

Affordably priced and familiar to most installers, mineral wool is one of the most popular categories.

“There are a few main types of mineral wool insulation, most commonly glass wool, slag wool and rock wool,” says Clive Holland, property expert and Fix Radio presenter. “Rock wool is made from volcanic rock such as basalt, while glass wool is made primarily from recycled glass, and slag wool is produced from blast furnace slag."

He adds: “All of these types of mineral wool have a similar fibrous texture, but rock wool tends to be denser and more robust, which gives it an edge in several performance areas.”

The processes for manufacturing most mineral wools are broadly similar. Raw material is melted, then spun into fibres which are bound together into an insulation product such as a roll.

We should clarify that ‘Rockwool’ is the brand name of one particular rock wool producer. This is not the only brand making rock wool insulation (originally known as ‘stone wool’), but its name has become a byword for rock wool itself, much like other genericides such as ‘hoover’ for vacuum cleaning and ‘google’ for searching the internet.

Which is better: rock wool or other mineral wools?

Thermal insulation

In terms of thermal performance, there’s not much to choose between rock wool and other types of mineral wool such as glass wool.

According to insulationgo.co.uk, certain examples of the two types can have the same thermal conductivity, rated at 0.044 W/m·K. However, glass wool is assessed as providing a higher R-value (better resistance to heat flow), at 3.2 m²K/W compared to rock wool’s 2.27 m²K/W.

With that said, thermal insulation performance varies depending on the specific product (and its thickness). An exceptionally insulative rock wool product might outperform the average glass wool insulation when it comes to keeping you cosy. So, it's always worth researching the rated performance of mineral wool insulation products (several are listed here at B&Q) before you choose one.

Winner: other mineral wools such as glass wool (but it’s a close contest)

Acoustic insulation

Holland suggests that rock wool is the superior option for acoustic insulation, with “extremely effective soundproofing performance”.

This is due to the far higher density of material in rock wool insulation, when compared with glass wool especially. One cubic metre of rock wool can weigh as much as 200kg, whereas the same volume of glass wool insulation would tend to weigh no more than 110kg.

“With regard to sound, rock wool excels over glass wool, and all other forms of mineral wool, as an insulating medium,” says Jake Fry, founder of Smallworks.

“This is because its denser fibrous structure absorbs sounds most effectively, leading to the reduction of noises, both by air and also by impact from the other side of the insulated surface.”

Fry recommends choosing rock wool to insulate properties close to sources of unwanted noise, such as flats.

“It’s effective at insulating the space from both higher and lower sound frequencies, whereas a less efficient material such as glass wool would not meet the same soundproofing requirements,” he says.

Winner: rock wool

Durability & safety

“Rockwool’s durability is a big plus – it holds its shape over time and doesn’t sag or deteriorate as easily as other materials,” says Holland.

“It also offers superior fire resistance, which makes it an excellent choice for improving a home’s safety, and it’s extremely effective at managing moisture, which helps prevent damp or mould issues.”

Electrician, Daniel Vasilevski of Pro Electrical, agrees that rock wool has the edge when it comes to fire safety – although many mineral wool products provide some benefits in this regard.

“There are distinct safety advantages of mineral wool, especially basalt-based products [which are an example of rock wool], as it has resistance to both heat and flame spread. This becomes important when running wiring in wall cavities or ceiling spaces.”

Winner: rock wool

Convenience

Mineral wool – including rock wool – is generally considered a relatively easy form of insulation to install. Which product will be simplest to put in place depends on the project.

“Rock wool is denser and holds its shape better than glass mineral wool, and this makes it more stable in running electrical circuits in walls or ceilings – it will not shift as easily, so it gives better conduit and cable support over time,” says Vasilevski.

“But at the same time, because rock wool is denser it becomes a little more difficult to cut or to fit against junction boxes than glass wool, which is softer and more pliable.

“While rock wool has advantages, glass wool will be a bit easier to handle in detailed work,” he adds.

Whichever type of mineral wool insulation you choose, you’ll need to be careful when handling it.

“Always wear gloves, long sleeves, and long trousers to protect your skin, and a dust mask to prevent breathing in fine fibres,” says Holland.

“Poor handling can cause irritation to both skin and airways, so taking basic precautions is essential – particularly for DIYers.”

Winner: varies depending on project specifics

Environmental impact

Neither rock wool nor other mineral wools tend to be particularly eco-friendly, due to the carbon-emmissive processes involved in their manufacture (for most products of these types). However, certain products have lower environmental harms or better mitigations than others.

“Rock wool often incorporates recycled steel slag, which helps reduce waste and makes it one of the more environmentally responsible options on the market,” says Holland.

Meanwhile, Earthwool branded insulation (like these examples sold via Amazon) is a glass wool option made mostly from recycled glass, which gives it a relatively small ecological footprint.

Several insulation materials are regarded as better for the environment than mineral wools of any type. These include cork insulation, sheep wool, straw bales and hemp.

Winner: it depends on the product

Three types of mineral wool to consider:

How to choose the right mineral wool insulation for your project

Rock wool slightly outperforms other mineral wools including glass wool when we consider the materials’ thermal performance, acoustic performance, durability and convenience, all together.

“Rock wool stands out for its all-round performance, but the downside is that it’s more expensive than glass wool or slag wool, so for large projects the upfront cost can be a consideration,” says Holland.

“Glass wool, for example, is much cheaper and still provides good thermal insulation, though it doesn’t perform as well in terms of soundproofing or moisture resistance.”

Regardless of its higher price, rock wool remains Holland’s personal recommendation, based on its superior durability and all-round performance. He suggests consulting an expert to find the ideal product for your property.

“If you’re a DIYer, take a few photos of your loft or the area you’re insulating and speak to your local builders’ merchant or DIY outlet – they can help you find the right product for your budget and project,” he says.

FAQs

How is mineral wool insulation used in properties?

Mineral wool insulation is a versatile category of materials, sold in various formats to suit different domestic applications.

It is often used as cavity wall insulation or internal wall insulation, as well as in pitched or flat roofs and as loft insulation. Rock wool, in particular, is popular as a noise-reducing cavity wall insulation material in properties which are near roads or other sources of noise pollution.

Mineral wool pipe insulation is used around pipework to prevent heat loss and freezing.

What are the benefits of installing mineral wool insulation?

Adding mineral wool insulation to floors, walls or other parts of a building can bring structural, energy efficiency and quality of life benefits.

“Mineral wool, in any form, is a great all-rounder for building insulation, providing strong thermal performance, helping to keep heat in during winter and out during summer,” says Holland.

“It also contributes to energy efficiency, cutting your heating bills and carbon footprint. Its soundproofing qualities are another major advantage, and most types provide an added layer of fire safety as they are non-combustible.”

Holland notes that it could be worth investigating your household’s eligibility for a government grant to help with the costs of insulation – especially if your home is not currently insulated.

“Speaking to a local service provider is the best way to check eligibility and get the process started,” he advises.

Feeling the chill? Take a step towards a warmer home with our guides to conservatory winterproofing, economical central heating habits, and how to get maximum heat from a wood-burning stove.

Expanded cork insulation is one of the eco materials of the moment, with proponents ranging from RIBA to NASA.

You might be wondering if cork insulation could suit your self build project or energy-efficient home renovation. Is it truly eco-friendly, what makes it a good for home insulation, and which forms of cork insulation are available in the UK?

To answer these questions and learn about cork’s insulative thermal and acoustic properties, we interviewed the world’s leading cork producer, and an award-winning architectural firm which has made headlines with its cork-clad projects.

What is cork insulation?

When we think of cork, many of us will picture a cork – the stopper in a wine bottle. This is essentially the same material used to make cork insulation.

Amorim Cork Solutions is a sub-brand of the world’s largest cork producer, and the bulk of its insulation products are made from waste cork left over from bottle stopper production.

“Stoppers are our main business, but we produce different types of products as Amorim Cork Solutions, and one of these is expanded cork insulation,” says Edgar Nadais, head of sales to the construction industry. “We take the branches of the tree, which are not used to produce the stoppers, and we make these into granules which are then treated with heat and pressure in an autoclave.”

This process extracts the cork’s resin, which acts as a natural binder to form the cork into a solid piece.

“We cut the blocks into several thicknesses to suit different purposes, mainly for use as insulation,” says Nadais. “From the raw material to the final block, the whole process takes about 20 minutes.”

This efficient use of waste cork is one reason why expanded cork insulation is considered an eco-friendly alternative to other materials such as mineral wool. Very little intervention is required to turn the branches of the cork oak (quercus suber) into an effective insulation product.

Cork science: why is it a good insulator?

Cork has a honeycomb-like structure of hexagonal cells. The cells trap pockets of air, which has low thermal conductivity and therefore limits heat transmission.

This accounts for cork’s thermal insulativeness – but according to Nadais, it’s the material’s density that makes the difference to its acoustic insulation.

“When you compare expanded cork with a traditional synthetic insulation, the cork is about five times denser,” he says.

More material typically means superior soundproofing, as a soundwave will require more energy in order to pass through the denser matter.

What are the benefits of cork insulation?

Cork insulation is not widely installed in the UK, but Nick Newman, Founder of Studio Bark, believes there’s potential for growth in its use.

“I think that as a result of cork insulation’s technical, environmental and [when used as cladding] aesthetic qualities, we will start to see it more and more,” says Newman, who has used cork extensively in acclaimed projects such as The Cork Studio.

Increased usage of expanded cork insulation could be good news for our buildings (and the environment), as the material has numerous benefits.

Most obviously, it’s an effective thermal insulator, with a lower thermal conductivity than that of rock wool insulation. The potential reduction in heat loss should mean lower energy usage, cheaper bills and cosier indoor temperatures.

Cork is also notable for its acoustic insulation performance. The material has been found to absorb up to 70% of sound, and therefore reduces noise transmission through walls and other surfaces.

If, like many buildings in the UK, your property is prone to damp and mould, then using cork insulation could play a part in managing these issues, as the material is naturally resistant to moisture transmission (one reason for its use as wine bottle stoppers) and breathable.

You might have some concerns over the fire safety of cork, given that it’s a type of wood. However, the material is relatively fire resistant when compared with other wood products. It burns slowly and does not produce a flame.

Cork is surprisingly durable. Much like memory foam, it has high viscoelasticity, which means it can flex and return to its original shape after it is compressed. (You’ll know this if you’ve ever tried to persuade a champagne cork back into the bottle.)

But the most important benefit of cork insulation, many would say, is the combination of its insulative properties with a relatively low environmental impact. While any effective insulation product provides eco benefits by limiting the need to use energy for heating, insulating with a natural material like cork does the same without causing the environmental harms associated with synthetic insulation production.

If you’re aiming to self-build a home that meets Passivhaus criteria, then cork would be one of the best qualifying choices for your insulation.

Another advantage to using this natural insulation material is that it’s non-toxic and hypoallergenic.

“Many people are unaware that some synthetic insulation materials are not allergy-friendly,” says Nadais. “Choosing expanded cork can be a good decision for your health, as well as your home.”

Types of cork insulation and their applications

Expanded cork insulation is produced in various forms to suit different uses and requirements. Popular types include:

• Boards or panels. These are used for insulating walls, rooves, and floors. Various thicknesses are available, and many examples can be used either within a wall or as an external cladding.
• Rolls. Thinner than boards, these products are most commonly used in smaller structures where space is limited, or as underlay for flooring.
• Granules: Used to fill gaps in ceilings, floors, and cavity walls.
• Spray: Cork is added as an insulative surface layer in the form of a spray.

Cork insulation options for your home:

Installation considerations

Using expanded cork insulation tends not to add much complexity to construction or renovation, but there are considerations to be made in some cases.

“The main methods for installing it are either as external wall insulation (EWI) or as a rainscreen cladding,” says Newman. “When using it as EWI – for example, over masonry – this might involve putting a parge coat over the brick for airtightness and levelling, and/or an adhesive. If using an adhesive, the type chosen will impact on the reusability and biodegradability of the insulation.

“For rainscreen cladding installations it can be fixed with batten and counter batten in a similar manner to traditional cladding,” he adds. “Stainless cladding crews can be fixed through the boards, and the heads can be hidden slightly below the surface of the cork, which springs back into place.”

Should you choose cork insulation for renovation or self-building?

There are transformative advantages to using expanded cork insulation, rather than a more commonplace synthetic option. As Newman puts it: “Cork is really an incredible, versatile material. It is naturally water resistant, needs no coat on top of it, has acoustic properties and can create a beautiful, matt finish.

“It is also 100% biodegradable if expanded cork is specified (as opposed to agglomerated cork, a type used in products such as corkboards).”

No building material is without its flaws – and in cork’s case, the main issue is the initial expense. Before VAT, a single 50mm-thick, 3-square-metre panel can cost upwards of £80. That’s more than ten times the price of certain mineral wool insulation products.

“It’s true that you’re spending more at the outset, but if you do the right calculations factoring in the lifetime of your house, you are saving money in the long run,” says Nadais. “In the end, you’re choosing a product that will perform better than others and has higher durability.”

Many examples of expanded cork insulation are fully recycled, fully recyclable, and therefore carbon-negative. Factoring in its eco credentials, there’s a compelling case to place cork insulation at the heart of your home.

Carefully chosen materials are fundamental to a home’s aesthetics, performance and environmental impact. For further eco-friendly inspiration, see our features on recycled plastic mortar, denim insulation and Irish moss lawns.

If you’re looking for the answer to what is insulated plasterboard you’re in the right place. In easy-to-understand terms, it’s a smart, dual-purpose material that combines plasterboard and insulation into one neat package. It's ideal for retrofits, renovations and conversions.

Once fitted, you can select any type of plaster to finish, ready for painting or wallpapering. Here, we briefly explore what it is, examine the science behind the insulation, discuss the different types, look at the popular choices, and identify which is the most cost-effective option.

What is insulated plasterboard?

The term insulated plasterboard (sometimes also called thermal plasterboard) refers to a specific type of plasterboard and insulation. Thomas Oldham, Co-founder of UK Construction Blog shares a brief explanation, “Insulated plasterboard is a combination of standard plasterboard with a layer of insulation bonded to the back.”

He adds, “It gives you a smooth, ready-to-finish surface while helping to keep your home warmer, all without losing much room space. It’s an excellent way to boost energy efficiency when you don’t have the depth for traditional insulation.”

Tom Hall, Category executive at Kingfisher Direct, points out, “It significantly reduces installation times and provides cost-saving benefits by preventing the separate installation of plasterboard and insulation.”

Try these insulated plasterboard options

The science behind the insulation

The integrated insulation layer in insulated plasterboard is where the magic happens, as Hall explains, “PIR insulation reduces the transfer of heat through a building's structure due to its closed-cell structure that creates a barrier preventing the movement of heat through the material.”

He adds, “The foam contains small interconnected cells that contain air or gas. This air serves as a thermal barrier, creating a resistance when heat tries to pass through the insulation”.

The same principle applies to EPS (Expanded Polystyrene) and phenolic foam. In simple terms, all three options keep the warmth in during colder months and the heat out during warmer months.

Oldham adds, “Phenolic foam tends to offer the best insulation for its thickness, while PIR and EPS strike a solid balance between cost and performance.”

Key benefits of insulated plasterboard

Whatever type of insulated plasterboard is being used, it offers many benefits, some more obvious than others.

Energy efficient

Oldham says, “From experience, the main benefits of insulated plasterboard are its practicality and efficiency. It makes a noticeable difference to indoor comfort and helps reduce heating bills.” It directly addresses heat loss through walls (up to 25%).

Hall reinforces the point, “Insulated plasterboard has higher thermal efficiency as it traps heat, which helps to keep your home warmer in the cold weather. This reduces the reliance on heating systems, lowering energy usage and the cost of bills”.

In addition, it will help eliminate drafts and cold spots.

Easier installation

Hall says, “Due to its two-in-one nature, it’s much easier to install than separate layers of plasterboard and insulation.” He adds, “Simplified installation makes it a much more cost-effective choice due to reduced labour costs, as well as lower material costs.”

Typically, you’ll only need screws and a drill to fix. Alternatively, a grab adhesive can be used for a quick and easy installation.

Space saver

The combination of plasterboard and insulation, or just insulation, can make it a real space-saving option. Hall says, “It eliminates the requirement for a separate layer of insulation, which can be highly beneficial in smaller properties where space is limited.”

Types of insulated plasterboard

PIR plasterboard

PIR (Polyisocyanurate) plasterboard is the insulated plasterboard commonly associated with the term. It boasts a rigid foam board that provides high thermal efficiency. This is typically bonded to the back of standard gypsum plasterboard.

This creates a thinner profile, often 37.5mm thick with board and foam. Some PIR boards are faced with foil to improve insulation and act as a vapour control barrier. Typically more expensive than other types, such as EPS.

EPS insulated plasterboard

Expanded Polystyrene plasterboard is similar to PIR plasterboard. Instead of a rigid foam backing, it uses an expanded polystyrene backing that is bonded to gypsum plasterboard. It’s a versatile product that is good for larger areas and is typically cheaper than PIR board.

Phenolic foam

Phenolic foam is a board made from a rigid, closed-cell insulation material. It has high thermal efficiency and typically features foil on both sides to protect the insulation from moisture. Unlike PIR and EPS, it is not bonded to gypsum plasterboard. It comes in various thicknesses and can be more expensive than PIR and EPS depending on the chosen thickness.

Moisture resistant boards

Insulated plasterboard and board include a foil backing to provide a vapour barrier, helping keep the insulation dry and combating moisture and condensation at the same time.

Applications of insulated plasterboard

Insulated plasterboard and its variants are versatile and can be used almost anywhere in a home. Oldham points out a few of its typical uses: “I recommend using insulated plasterboard on internal walls, ceilings, and loft conversions.”

He adds, “But it’s equally useful for garages, garden offices, or extensions that need better temperature control.”

However, depending on what type of insulated plasterboard you are using, it can be used elsewhere, as Hall shares, “It can be used to line external brick walls due to their poor insulating properties.” This makes it ideal for older properties or single-skim walls that lack good insulation.

Hall adds, “They can also be used internally to line floors, walls and ceilings. In particular, they are popular for lining walls and ceilings in loft conversions due to their thinner profile that helps to maximise space”.

Considerations for Installation

When installing insulated or thermal plasterboard, there are a few simple considerations to keep in mind.

Thickness of board

In simple terms, the thicker the insulation, the more efficient it will be. But this depends on the type of board being used. PIR board commonly uses 25mm insulation, while EPS and Phenolic foam board can be purchased in various depths from 25mm to 100mm.

The thicker the board, the more space it will take up in a room; this is especially important to note if indoors.

Cutting and installation

To cut plasterboard, you will need a long, straight edge and a sharp utility knife (like this Amazon Basics Durable Folding Utility Knife). Use this to score the board and finish with a saw. You can use a hand saw or a jigsaw (like this Bosch Home and Garden Jigsaw from Amazon) to cut the board and the insulation.

Installation depends on the surface it is being attached to. The dot-and-dab method or a suitable adhesive are common choices for block walls. If attaching to timber, use plasterboard screws.

Continuous vapour barrier

When using foil-backed or covered board, gaps between fitted boards will allow moisture to seep in. To stop this happening, you will need to use an insulation seam tape like this Gladiator Aluminium Tape from Amazon.

The beauty of insulating plasterboard is that you can finish putting it up in double quick time. Once installed, it’s time for the next steps. Find out how long it takes t plaster a room, before you think about painting new plaster and choosing the right wallpaper tools to finish a room.

Those looking into how to insulate floors in an old house will probably already be aware of the positive impact that this job can have. Not only will it improve how well a house retains heat, but it can also lower energy bills and, of course, make walking around in bare feet much more pleasant.

If you are in the process of renovating old floors it makes sense to investigate what type of insulation, if any, is currently lurking beneath. In many cases, the floors of older homes were not insulated at all, leaving them feeling decidedly chilly underfoot. That said, modern homeowners need to be careful that by adding modern insulation they don't cause issues elsewhere in the house.

With the help of some insulation experts, our guide explains everything you need to know about insulating old floors, including the best techniques and materials to use – as well as vital advice on when to leave well alone.

Is insulating old floors necessary?

Insulating old floors can be disruptive meaning it is a job many homeowners, even those renovating a house on a large scale, are keen to avoid – but there are some good reasons to tackle the task.

"The primary reasons for insulating older ground floors are the significant improvement in internal comfort, achieved by reducing cold spots and eliminating draughts," explains Samuel Hitch, MD of Buy Insulation Online. "Also, the energy savings can typically amount to approximately £70 to £80 annually."

"Floor insulation can reduce heat loss by 10-15%," adds Zaeem Chaudhary, director and Chartered Architectural Technologist (MCIAT) at AC Design Solution. "However, it's not always advisable – the decision depends on the building's construction and condition."

What type of floor construction are you dealing with?

There are two main types of floor construction homeowners of old houses are likely to be faced with: suspended floors and solid floors.

Suspended floors are very common, both at ground and first floor level and, when uninsulated or poorly insulated, are a common cause of cold draughts. They are made up of timber floorboards sitting on top of joists that rest just above the foundations in the case of ground floors, or on the ceiling joists of the rooms below when it comes to upper storeys.

Solid floors are also frequently discovered in old houses, predominantly at ground floor level. They can be as basic as block parquet, flagstones or quarry tiles laid over nothing more than compacted earth or ash. Where an old house saw solid floor repairs during the post-war years, concrete floors are not uncommon, seen as a way of reducing drafts but often overlooking the need for breathability.

Insulating suspended timber floors

As the potentially draughtiest type of old floor, it makes sense to begin by looking at the best ways of insulating suspended structures – a job likely to be on your to-do list anyway if you are looking at how to insulate a Victorian house.

"These floors are insulated by placing material between the joists," picks up Samuel Hitch, who goes on to explain that the two most common ways of doing this are either from beneath or above the floor.

"Installation from beneath, for example from cellars or crawl spaces, is the ideal method, as it avoids damage to the original floorboards," says Samuel. "Flexible, vapour-open insulation (such as mineral wool or natural fibre) is secured between the wooden joists using netting, timber battens, or a breathable membrane. A crucial, non-negotiable rule is that a clear space of at least 150mm must be maintained below the insulation to ensure continuous cross-ventilation and prevent timber rot.

"Installing insulation from above requires carefully lifting the floorboards," continues Samuel. "Once the insulation is in place, draught-proofing is vital: gaps between the reinstated boards and skirting boards should be sealed using compressible foam rods, papier mâché, or small slips of timber."

Shop insulation for suspended floors

Insulating solid floors

Solid floors can present a few more issues when it comes to adding in insulation than their suspended counterparts. This due to the importance of maintaining breathability and natural ventilation, something that solid floors laid on earth or ash allow.

"The simplest method involves laying a 'floating floor' on top of the existing slab. This uses rigid, high-compressive-strength insulation boards (such as PIR or EPS) laid directly on the concrete, followed by a new floor surface. However, this method will raise the floor level, requiring adjustments to doors, skirting boards, and thresholds," explains Samuel Hitch.

But what about when it comes to heritage properties that rely on breathable finishes, such as lime mortar, or listed buildings in which original flooring must be retained?

"If the existing slab must be removed, the new substructure needs to be 'vapour-open,'" explains Samuel Hitch. "Systems include limecrete or specialist alternatives like a pozzolanic hydraulic binder (lime mixed with crushed brick dust) over an insulating sub-base of foam glass aggregate. Foam glass aggregate is vital as it provides both insulation and a primary capillary break, allowing the floor to drain water away from historic walls.

"If historic flagstones or tiles must be preserved, surface insulation can be applied," continues Samuel. "This requires a 'capillary break layer' (CBL) to first interrupt rising damp, followed by capillary-active, vapour-open boards (such as expanded cork or wood fibre). These materials actively buffer and transport moisture, protecting the historic structure from damp accumulation."

Can insulating old floors do more harm than good?

There are instances where to add insulation to old floors can actually cause more issues than it solves, including mould under flooring.

"The most serious structural risk when retrofitting older properties is the management of moisture. Insulating a floor cools the underlying void, increasing humidity and creating conditions that are ripe for timber decay and rot," warns Samuel Hitch.

"It is better practice to leave a suspended floor uninsulated than to compromise the ventilation system, as insufficient airflow will inevitably lead to moisture accumulation and structural decay," continues Samuel. "It is structurally essential to maintain adequate sub-floor cross-ventilation, typically via air bricks.

"In the case of solid floors, particularly in protected or listed buildings, if the intervention involves modern, impermeable materials (such as standard plastic damp-proof membranes or certain rigid foams), it is often safer to avoid the work entirely," adds Samuel. "These non-breathable barriers can displace ground moisture into adjacent walls, causing rising damp and salt damage. In any case, energy savings for solid floors are often marginal anyway due to the stable temperature of the ground beneath."

Why type of insulation should be used to insulate old floors?

It's clear that insulating old floors needs to be carried out with care in order to ensure this is a job that's both worthwhile and beneficial. This also means selecting the right type of insulation for the job.

"For suspended floors use flexible, vapour-open materials, such as mineral wool, sheep's wool, or hemp/jute fibre," advises Samuel Hitch. "For some solid floors it will be fine to use rigid boards, such as PIR or EPS (good for compressive strength), but if you are dealing with breathable systems you'll need to use something else.

"Expanded cork board, wood fibre board, limecrete and foam glass aggregate are all options," continues Samuel. "Impermeable materials such as standard DPMs and many rigid foams are unsuitable for traditional structures."

How much does it cost to insulate old floors?

Insulation costs vary depending on the type of floor structure you are dealing with, as well as the size of the area that needs work.

"The total cost for an average UK home is approximately £6,000," advises Samuel Hitch. "Costs per square metre vary. For example, a floating solid floor system is the cheapest at approximately £70 per square metre.

"Standard suspended floor insulation costs around £105 per square metre, but this can increase sharply to around £258 per square metre if structural timber repair or floorboard replacement is required due to rot. Specialist heritage work is significantly more expensive due to complex materials and highly skilled labour."

How should you deal with pipes and wires when insulating old floors?

It is not unusual for a selection of service pipes and electrical cables to be run through floors and it is important to take care not to damage these when upgrading insulation.

"Services must be managed according to safety standards (BS 7671)," points out Samuel Hitch. "Electrical cables running through thermal insulation can overheat, increasing fire risk. The safest practice is to relocate cables outside the insulated void or to replace them with higher capacity cables. If cables must penetrate the insulation, they should be routed at a right angle to minimise contact.

"Water pipes in the newly cooled sub-floor void must be properly lagged to prevent frost damage and condensation on cold water pipes," continues Samuel. "Central heating pipes should also be lagged to prevent heat loss. Additionally, holes drilled through joists for services must pass through the centre line of the joist to maintain the structural integrity of the timber."

FAQs

What are the building regs for floor insulation?

When it comes to insulating your old floors you need to be aware of the building regulations surrounding this element of the home – information that can be found in Part L.

"UK building regulations require that an existing floor undergoing thermal upgrades must achieve a limiting U-value of 0.25W/m2K," says Samuel Hitch. "This means installing approximately 110mm to 120mm of standard insulation. In suspended floors, the structural requirement to maintain the 150mm ventilation gap takes precedence over strictly meeting the U-value target if there is a conflict. Protected properties also require Listed Building Consent (LBC)."

With your insulation in place, it is likely you'll want to get any original flooring looking as good as when it was first installed – our guide to repairing wood flooring is the perfect place to start.

A damning new report has found that nearly all homes fitted with external wall insulation under government energy schemes could now be at risk of damp and mould.

The National Audit Office (NAO) uncovered widespread failures in workmanship and compliance across the Energy Company Obligation (ECO) and the Great British Insulation Scheme (GBIS).

The government has promised swift action, but campaigners warn that thousands of families are already living with the consequences of poor installation and weak oversight.

Widespread installation failures

The NAO report reveals major quality problems in homes retrofitted under ECO4 and GBIS, with external and internal wall insulation accounting for thousands of non-compliant installations.

TrustMark, the government-endorsed quality scheme, informed the Department for Energy Security and Net Zero (DESNZ) that high levels of work were substandard, posing risks ranging from poor insulation performance to damp and mould.

“The urgent priority for government should be to ensure faults are rectified and households have the warm, safe and healthy homes they were promised,” said Adam Scorer, Chief Executive of National Energy Action (NEA).

“People should have peace of mind that work in their homes is completed to a high standard, and where it is not, mistakes are corrected quickly at no cost to them.”

According to the report, 28,000 homes have had external wall insulation installed, representing just 3% of all measures, yet these are responsible for the majority of quality complaints and failures identified by TrustMark.

Suspected fraud and oversight failures

The report also highlights suspected fraud, with some retrofit businesses overclaiming for work not carried out or not meeting required standards.

TrustMark notified DESNZ of the issue in April 2024, warning that undetected fraud meant fewer households benefitted from the schemes than reported.

The NAO concluded that weak oversight and fragmented responsibility between DESNZ, Ofgem, and private contractors allowed both poor quality work and fraud to go unchecked.

The watchdog said the government’s monitoring system had “limited information and few levers” to prevent widespread failure.

Government response and next steps

The Department for Energy Security and Net Zero said it has taken immediate action to ensure that all affected homes are identified and remediated.

“Installers responsible for this substandard work will be forced to fix it and households should not be asked to pay,” said a DESNZ spokesperson, echoing the government’s position in a recent statement.

DESNZ added that it is reviewing how retrofitting schemes are managed to strengthen consumer protections and prevent future fraud.

“Effective insulation remains vital to tackling fuel poverty and cutting emissions - but these failures show that delivery must match ambition,” added Adam Scorer of NEA.

With over 300,000 homes upgraded under ECO4 and GBIS combined, ministers now face mounting pressure to prove that taxpayer-funded retrofits are both safe and genuinely energy-efficient.

If you have discovered wet loft insulation in your roof space you are likely to be wondering how it got that way. Insulation is so important in keeping your home at a comfortable temperature, as well as helping to reduce household bills, but there are cases where its effectiveness can be compromised.

There are several reasons why loft insulation gets wet or holds on to excess moisture. Understanding what these are, finding the culprit of your particular problem and getting to grips with how to prevent it from reoccurring is vital if you want the insulation to do the job it is there for.

We reached out to the experts to discover the leading causes of wet loft insulation and what can be done to both fix the issue as well as the steps you can take to stop it from happening in the first place.

Why is my loft insulation wet?

If you notice your loft insulation feels damp to the touch, or is visibly wet (look for dark patches, mould and areas of sagging), you are likely to be pretty concerned. There are two main reasons why this issue might have occurred: condensation and leaks in the roof structure.

"The most common cause of widespread dampness in loft insulation is internal condensation in lofts – not necessarily a roof leak," reveals Samuel Hitch, MD at Buy Insulation Online. "This occurs when warm, moist air generated inside the house (from cooking, washing, etc.) escapes into the cold loft space."

"Condensation is almost always the root cause and poorly installed insulation can create this effect," adds Zaeem Chaudhary, director and chartered architectural technologist (MCIAT) at AC Design Solution. "That's why modern buildings tend to use warm roof construction or cavity walls rather than cold decks and hybrid roof systems."

"Condensation presents as diffuse dampness across broad areas of the insulation or roof deck, often worsening during cold, dry weather when the temperature difference between the house and the loft is greatest" adds Samuel Hitch.

The good news is that once you have pinned down the root cause of your wet loft insulation, there are steps you can take to put the problem right.

What causes loft condensation?

With condensation being the leading cause of wet loft insulation, it is important to understand why it occurs and what can be done to prevent it. The first issue to be aware of is poor or compromised ventilation.

"Continuous ventilation is mandatory,' picks up Samuel. "UK Building Regulations guidance requires continuous cross-ventilation in cold pitched roofs to disperse moisture vapour before it can condense. Effective moisture control hinges on maintaining two specific air gaps: eaves intake and rafter void.

"When it comes to eaves intake, an air intake equivalent to a continuous 25mm deep slot must be maintained at the eaves," further explains Samuel. "Purpose-made eaves vents or baffles are often required to achieve this.

"For the rafter void, a minimum 50mm continuous air path must be maintained between the top of the insulation and the underside of the roof deck or membrane to allow air to flow unimpeded from the eaves to the ridge.

"Installing deep layers of insulation (often around 270mm to meet thermal targets) can inadvertently block the critical 25mm eaves vent or the 50mm air path if installation trays or baffles are not correctly used," adds Samuel.

Finally, in some cases, vapour control layer (VCL) failure can be to blame.

"If the VCL, which should be on the warm side of the insulation, is missing, misaligned, or not meticulously sealed at all overlaps and penetrations, warm, moisture-laden air bypasses it and reaches the cold void, leading to interstitial condensation," explains Samuel Hitch.

What are the signs of a leaking roof?

Wet loft insulation is not always caused by condensation and it is important to be aware of this – an undetected leak could be to blame. The signs of this are very different to the kind of wetness you can expect from condensation.

"Leakage typically causes heavy, localised saturation directly beneath a defect, for example a missing tile, damaged flashing, or plumbing leak," explains Samuel Hitch. "It may also correlate with periods of heavy rain."

If you suspect a leak is causing your loft insulation to get wet, look out for missing or worn out flashing, slipped roof tiles, blocked gutters or damage to your chimney. The roof leak repair costs you incur will be well worth it to protect the rest of your home.

What happens when loft insulation gets wet?

When loft insulation gets wet, its performance is affected and it could, if left in this state, cause issues with the structure of your loft, including damp, rotten rafters and mould.

"Insulation traps air in tiny pockets," explains Zaeem Chaudhary. "Air doesn't conduct heat well, so it slows heat loss. When it gets wet, water fills those air pockets and water conducts heat about 20 times better than insulation. Research shows that just 20% moisture can cut the performance of insulation by half. The insulation also gets heavy, compresses, and loses its structure."

"Wetness destroys thermal performance," reasserts Samuel Hitch. "Regardless of the material, water dramatically increases its thermal conductivity, effectively causing the wet insulation to stop resisting heat flow and rendering it thermally ineffective."

Are some types of insulation more prone to damp than others?

While ensuring good ventilation and keeping on top of roof maintenance are both good ways to ensure your insulation stays dry, it is interesting to note that the type of roof insulation you choose can play a part too.

"The common fibrous materials perform differently: stone wool (Rockwool) is highly moisture-resistant, retains its structure when wet, and has good drying potential," explains Samuel Hitch. "Glass wool (Fibreglass) is less resistant, can easily get damp, and may promote mould growth, as well as suffering from severe thermal loss if left saturated."

Should wet loft insulation be dried out or removed?

Once you have discovered wet loft insulation, what should your next steps be? If you act quickly, it might not be necessary to look into insulating a roof all over again.

"Immediately identify and fix the source of the moisture – most likely a leak or ventilation failure," begins Samuel Hitch.

"Next, carefully remove wet mineral wool and dry it thoroughly in a warm, well-ventilated area. If the dried material is structurally compromised, retains a persistent odour, or has suffered chronic saturation, it must be replaced to protect the structural integrity of the roof timbers.

"Finally, use fans and dehumidifiers to dry the surrounding loft structure," adds Samuel.

Shop dehumidifiers

FAQs

Will boarding a loft stop insulation getting damp?

Boarding a loft is not only a great way to transform it into extra storage space – it can also add value to your home as well as ensuring the area stays moisture free.

'To prevent damp loft insulation, it’s recommended that you board your loft, which helps trap heat,' explains Andy Simms of MyBuilder.

It helps to understand how moisture gets into your loft in the first place.

'Moisture enters the loft primarily through convective air movement –warm air escaping through unsealed gaps, cracks, and service penetrations in the ceiling,' explains Samuel Hitch. 'This transports far more moisture than slow diffusion through solid materials.'

'Daily activities create moisture,' adds Zaeem Chaudhary. 'The biggest contributors are drying clothes indoors, long showers and boiling pans without lids. Even breathing and houseplants add up.'

If you are ready to turn your loft conversion ideas into reality, be sure to discuss insulation with your builder or loft conversion specialist to ensure your newly formed space is neither too hot or too cold and is a pleasure to spend time in all year long.

Just how much does cavity wall insulation cost? If you are considering adding it in or upgrading existing insulation, this is likely to be a consideration for you right now.

Cavity wall insulation can be one of the best ways to reduce heat loss in a home, yet bad installation, the wrong materials and and using it where it is simply unsuitable can render that initial outlay worthless.

"According to our research, about 33% of all the heat lost in an uninsulated home escapes through the walls," reveals Richard Northcott, knowledge manager at Energy Saving Trust. "By installing cavity wall insulation, you can save energy and reduce your heating bill."

Our guide explores how much it costs to buy and install cavity wall insulation, the factors that can affect these figures and the potentially expensive mistakes to be aware of.

How much does cavity wall insulation cost?

Costs for insulating a wall vary greatly, depending on a number of factors, including, fairly obviously, the size of your house.

'The cost is not uniform, varying significantly by property type,' picks up Samuel Hitch, MD at Buy Insulation Online Ltd. "While the material cost for retrofit insulation (such as blown beads or foam) generally ranges between £13 and £30 per square metre, the final total price is much higher.

"The total average cost for a mid-terrace home is approximately £1,500, rising to around £2,700 for a semi-detached house, and up to £4,600 for a detached home," continues Samuel. "Professional labour often accounts for up to 60% of this overall project price. A pre-installation borescope survey, essential for compliance, can cost up to £300."

Are grants available for cavity wall insulation?

The good news is that, in some cases, financial help might be available to those looking at adding in cavity wall insulation.

"In England, Scotland or Wales, you might be eligible for funding via the Great British Insulation Scheme (GBIS).," advises Richard Northcott. "This is a government-backed scheme to upgrade the least energy efficient homes across Great Britain.

"Cavity wall insulation is the most common measure installed via GBIS, accounting for 45% of all measures installed."

What happens if cavity wall insulation is poorly installed?

If you are going to the not-inconsiderable expensive of installing cavity wall insulation, you want to be sure that the job is done well.

"The consequences of poorly installed cavity wall insulation are severe and costly," warns Samuel Hitch. "The primary physical failure is moisture saturation, where water penetrates the external wall and is carried across the insulation material to the inner wall, effectively 'bridging' the cavity.

"This results in patches of penetrating damp, excessive black mould growth, and long-term risks such as the corrosion of critical wall ties," continues Samuel. "Critically, concerns over damp and structural damage resulting from poor CWI have led to some mortgage providers refusing to lend money on affected properties, severely impacting property value and saleability."

While poorly installed CWI can be put right, this comes at a cost.

"Remediation is expensive and invasive, requiring three main steps," explains Samuel.

• Extraction: Professional removal of the failed, saturated insulation. Costs start from approximately £1,680 for a typical semi-detached home and can escalate to as much as £2,520 for a typical detached property.
• External repair: Factor in repointing costs for the comprehensive remediation of the external walls, including repointing damaged mortar and sealing all cracks, to ensure the building envelope is watertight.
• Internal repair: Addressing internal damage, such as removing affected plaster and replacing it with a damp-resistant system.

Is cavity wall insulation the best option for your home?

In some cases, cavity wall insulation won't be the best type of insulation and, in this case, you'll obviously want to spend your money elsewhere.

"If your house was built after the 1920s, its external walls are probably cavity walls," explains Richard Northcott. "A cavity wall is made up of two masonry walls with a gap in between them. The outer layer is usually made of brick, while the inner layer will be made of brick or concrete block. Pre-1920, older, houses are more likely to have solid walls. A solid wall has no cavity: each wall is a single solid wall, usually made of brick or stone.

"Cavity wall insulation is suitable for many homes and many people have no issues following its installation," continues Richard. "But cavity wall insulation might not be suitable if your home is exposed to extreme weather or flooring, in a poor condition, if there’s a risk of your rooms overheating or if it has been constructed with narrow cavities, less than 50mm (usually in homes built pre-1920’s)."

"Homes built before the 1920s or 1929 are overwhelmingly solid-wall construction and are physically unsuitable," further explains Samuel Hitch. "Mid-terrace homes built after 1945 generally have a cavity, but those built in the 1930s require specific inspection."

Can cavity wall insulation be used within damp walls?

The condition of your walls and the cavity within the inner and outer layers can also affect the cost of installation – particularly in the case of damp.

"Existing dampness and damage do not merely complicate the process – they render the property unsuitable for CWI until full remediation is complete," points out Samuel Hitch. "If external defects are present, moisture penetration is ongoing. Installing insulation traps this moisture, preventing the wall from drying out and potentially shifting the dew point further inwards, which can greatly exacerbate the risk of condensation and mould.

"Additionally, if cavities contain accumulated rubble, dirt, or mortar debris at the base, this will act as a permanent moisture bridge," continues Samuel. "Any home with structural damage, such as cracks or defective pointing, must be repaired beforehand."

What are the different types of cavity wall insulation?

There are several options when it comes to the type of cavity wall insulation that can be installed – but the best ways to insulate your home will very much depend on the property.

"The materials used depend on the project type," picks up Samuel Hitch. "For retrofit projects with an existing cavity, materials are injected or blown in. These commonly include expanded polystyrene (EPS) beads, mineral wool fibre, and polyurethane or urea formaldehyde (PU/UF) foam.

"For new constructions or extensions, materials are installed as rigid sheets or slabs during construction," continues Samuel. "Examples include rigid polyisocyanurate (PIR) boards (such as Celotex CW4000) and dense mineral wool insulation slabs (such as Knauf DriTherm)."

Blown insulation tends to be the cheapest option, with rigid boards and slabs sitting at the higher end of the price scale.

"There is no universal 'best type' of CWI material," explains Samuel. "The 'right' type is defined by its compliance with the specific environmental and structural conditions of the property, including cavity width and the wind-driven rain exposure zone. The definitive measure is the BBA Agrément Certificate, which must explicitly cover the product's suitability for the measured site conditions. The 'wrong' type is any material installed without this rigorous verification or in a property that is physically unsuitable."

Does cavity wall insulation cause damp?

Never try to save money simply by specifying the cheapest type of cavity wall insulation – you could run into all kinds of problems that will only end up costing you more in the long-run, damp included.

"While CWI helps mitigate cold surface condensation by warming the inner wall surface, improper installation creates problems," explains Samuel Hitch. "Voids or gaps in the insulation, resulting from poor application, create thermal bridges (cold spots) that attract atmospheric moisture, significantly increasing condensation and black mould growth inside the home.

"Furthermore, if the material is used in a high-exposure zone for which it is not certified, saturation will occur, disrupting the wall’s moisture balance and leading directly to penetrating damp."

"A good installer should not block or seal any intentional ventilation such as underfloor grilles or airbricks as these help keep wooden beams and floors dry,' adds Richard Northcott. 'Wall vents and trickle vents are also important as they let small amounts of fresh air flow into rooms."

FAQs

How much lower can you expect heating bills to be with CWI?

As well as increased comfort levels, installing cavity wall insulation can also cut household bills – but by how much?

According to Energy Saving Trust, for the average detached house, annual savings of £420 can be expected, while a semi-detached house could see bills slashed by £240 per year.

What are the building regulations for cavity wall insulation?

As with most home upgrades, building regulations apply to cavity wall insulation. To ignore them could mean paying out later down the line to put work right. There are several approved documents to be aware of, as Samuel Hitch explains.

"CWI is governed by Approved Document L (Conservation of Fuel and Power) This mandates insulation continuity to avoid thermal bridging. The cavity wall insulation must extend below the damp-proof course (DPC) and at least 215mm (one full block height) below the underside of the floor structure/slab," says Samuel.

"Approved Document C (Resistance to Moisture) requires that the design accounts for resistance to moisture, meaning installers must assess the exposure of the building to wind-driven rain and ensure the external finishes are appropriate for the local climate zone."

How much does a survey for cavity wall insulation cost?

In order to ensure you are specifying the correct type of insulation and are spending you money in the right places, a survey is key and, if you are renovating a house, this becomes even more important.

"A detailed pre-installation survey, performed by a qualified professional using a borescope inspection, is mandatory for compliance" explains Samuel Hitch. "This inspection visually confirms the adequate cavity width (some systems require a minimum of 50mm), the absence of existing damp, and, critically, the lack of debris or mortar snots that would compromise the installation."

Expect costs of around £300.

When budgeting for any home upgrades, thinking about longevity is really important. Looking into how long insulation lasts will give you a good idea of how much value for money you are getting from your chosen materials and installation methods.

While most homeowners are familiar with the more common types of insulation such as mineral wool or fibreglass, there are also a host of other products included under the heading of eco insulation.

And while hemp, sheep's wool and cellulose may also be products you've heard of, denim insulation is one that might not be on your radar, but is in fact readily available to buy.

So what is denim insulation, and how could your favourite pair of jeans be transformed into a viable insulation product to keep your home warm? We asked the experts to unzip their knowledge banks to explain where, and how, denim can be used to insulate your home.

What is denim insulation?

As the name suggests, denim insulation is a home insulation product made from material. But, it's not always just denim that features in its make up, which means it is sometimes referred to as cotton insulation too.

"Denim insulation is a soft thermo-acoustic material comprised of 85% cotton and velvet fibres," explains James King, managing director of Unity Lime Products Ltd.

"The raw material is sourced by collecting, sorting, and shredding unwanted denim and cotton textiles. The fibres are then bonded using a small percentage of polyester fibre to form the final insulation product."

But what about the rivets, zips and other components in a pair of jeans? "Recycled denim clothing is stripped of items such as zips or buttons and is then shredded into small pieces which are then treated and pressed into insulation mats," expands Mike Storey, insulation expert and technical manager at UKFR Roofing & Insulation. "This means the final composition is primarily cotton."

As a result, it's considered an environmentally friendly form of insulation to use in your home. It comes in the form of batts or loose-fill insulation and the product you choose depends on how and where you want to use it.

Shop for eco-friendly insulation

Where can you use denim insulation?

Before considering denim insulation for your home renovation, extension or self build, it's important to understand where you can and can't use denim insulation.

"Denim insulation is primarily installed between timber or metal frameworks such as studs, rafters, joists, and partition walls," James King explains. "It can also be laid over joists for attic insulation, where one of its most notable benefits is how pleasant it is to work with – it causes no skin irritation when handled."

However, it's not a case of one product suits all spaces warns Mike Storey. "It can't be used in flat roofs or floors, as it does not have a high enough compression ratio," explains Mike. "And, when used as internal wall insulation, in some circumstances it must be paired with a vapour barrier."

If used as part of a breathable construction it does't need a vapour barrier, but in some applications, such as existing solid wall applications it would. "However, there are often far better options for internal wall insulation on solid wall constructions than denim or rockwool," says James.

"But, with timber frame kits, an airtightness membrane will suffice. I am currently working in an office using denim insulation between studs without a vapour barrier internally. Using a vapour barrier in breathable systems will negate many of the benefits of using the material in the first place," he adds.

Can denim insulation withstand damp and moisture?

On the question of moisture, if it is installed correctly, how does it stand up to some of the issues home insulation has to deal with such as moisture and damp?

"As it is a breathable product, correct installation is essential to maximise its benefits, including its hygroscopic properties – meaning it can absorb moisture from the air and help create a more comfortable indoor environment," explains James.

"So, when installed as part of an effective system, including proper home ventilation and other vapour-permeable building materials, denim insulation performs exceptionally well in environments where moisture, dampness, and the risk of mould are concerns."

One of its benefits adds James, is that "the natural fibres in denim can absorb and release moisture without compromising the structural integrity or thermal performance of the insulation, helping to maintain a healthy internal environment."

Although, as with every home, maintaining the correct humidity level of between 40-60% is still essential.

Denim insulation vs other types of insulation

Wondering which insulation product you can switch out and replace with a more eco-friendly version such as denim insulation?

"It's a viable alternative to several common types of insulation, typically installed between studs or rafters,' says James King. "For example, it can be used in place of glass wool for insulating cold roof loft spaces, or instead of mineral wool or Polyisocyanurate boards between studs and rafters in a timber-frame building."

On the flipside, if the rising costs for building a house mean you are looking to save some money, it won't necessarily work out to be the cheapest option.

"While it is not the cheapest option compared to fibreglass, for example," confirms James, "for those who wish to use sustainable products with low embodied carbon, it is an excellent choice and one of the most cost-effective sustainable insulation materials available on the market.

"For DIYers, it is also a pleasant product to handle and install compared to conventional insulations," notes James, "which can irritate the skin if appropriate protective equipment is not worn when installing them."

In order to explain the comparisons in more detail, Mike Storey recommends using the following table to identify which of the most popular eco insulation products will best suit your needs.

* Added chemical to prevent

** Binder is the only part that causes growth, plus added chemical to prevent

FAQs

Does denim insulation have good acoustic properties?

"Yes, denim insulation has excellent acoustic insulation properties," says James King, "and is highly effective in partition walls and between floor joists to improve sound performance in the home.

"A 45 mm batt installed in a metal partition, with acoustic plasterboard on either side, achieved a 46 dB reduction. Denim insulation has also been used to manufacture acoustic panels and for sound deadening in the automotive industry."

Should I use denim insulation?

How you choose of course will come down to personal choice and the specific needs of your project. In Mike Storey's opinion, "denim insulation is a viable alternative to other insulation products, but personally, I feel it's not a match for mineral wool. And from a thermal point of view, you need to remember that PIR boards are almost twice as efficient," he adds, "so you only need almost half the thickness."

On the other hand, James King would have no hesitation recommending denim insulation if you are looking for a sustainable product.

"Is it worth it? Absolutely," he says. "Denim insulation offers many benefits beyond simply preventing heat loss. From regulating humidity and storing heat to having low VOCs, it is an exceptional product that consistently receives positive feedback from those who have used it."

Keen to explore other more eco-friendly types of insulation? Check out our guides to cellulose insulation and sheep's wool insulation. Or, if it's something more specific you need, find out which types of roof insulation are best for insulating the top of your home.

More than 30,000 UK homes have received poor-quality insulation under the ECO4 and Great British Insulation Scheme (GBIS), Minister Miatta Fahnbulleh admitted – calling it a “systemic failure.”

Many of the affected properties are in lower-income regions, notably Luton and County Durham, where reports of mould, damp and crumbling walls have emerged.

The revelation has fuelled fears that flaws in Britain’s retrofit schemes are not isolated mistakes but part of a recurring pattern.

The scale of the failure

The government’s preliminary audit indicates that over 30,000 homes receiving wall insulation under ECO4 and the Great British Insulation Scheme (GBIS) – launched in April 2022 and May 2023, respectively – failed to meet required standards.

Reports of black mould, peeling plaster and unsafe living conditions have been particularly prolific in areas like Luton and County Durham.

One homeowner in Luton spoke of being unable to sleep in his bedroom due to extensive damp and mould, describing the experience as a “nightmare,” while local reports from County Durham echo similar distress.

Ministers have noted that these issues are primarily connected to solid wall insulation, while other measures under the same schemes – such as those administered through local authorities or social housing – show higher compliance rates.

Nonetheless, this sizeable failure has affected households across diverse regions, highlighting that the problem is not confined to one demographic or geography.

Echoes of past retrofit scandals

Earlier retrofit schemes, such as the Green Homes Grant and the Renewable Heat Incentive, similarly fell short of expectations.

The Public Accounts Committee branded the Green Homes Grant a “slam-dunk fail,” citing delays and shoddy work.

The Energy Security and Net Zero Committee also called out the stop-start nature of retrofit programmes, which has hampered long-term progress on home energy efficiency.

Against this backdrop, the current ECO4/GBIS debacle risks reinforcing public mistrust and jeopardising net-zero goals.

How has the government responded?

The government has committed to swift action. Ofgem has already begun writing to the approximately 60,000 households that received solid wall insulation under the schemes.

Many affected homes have already undergone on-site checks, and in early remediation efforts, 90% of identified poor-quality installations have been corrected at no cost to consumers.

To prevent future failures, the government is rolling out a series of reforms:

• Installer bans 39 companies have been suspended from conducting new work under government insulation schemes.
• Warm Homes Plan reforms The controversial rollout is being overhauled through the Warm Homes Plan, due this autumn. New standards include higher qualification requirements for installers, single-certification-per-measure to increase accountability, and the establishment of a Retrofit System Reform Advisory Panel, bringing together industry, consumer, and enforcement experts.
• Ongoing oversight The government says Ofgem and TrustMark are conducting more rigorous audits, with obligations that installers remediate defects. The government has also promised transparency and better guidance for consumers.

These actions signal a shift from reactive fixes to structural reform, aiming to safeguard quality and restore confidence in retrofit schemes, but their effectiveness remains to be seen.

When it comes to improving the energy efficiency of your home, insulation isn’t just helpful – it’s essential. It is the backbone of a warm, comfortable, and environmentally friendly home.

But with so many options available, figuring out the best ways to insulate your home can be overwhelming.

I've built my own home, as well as advising many others along the way, so whether you’re self-building, renovating, or simply looking to lower your heating bills, here's what I consider to be the best ways to insulate your home.

Benefits of insulating well

A well-insulated home keeps the heat in during winter and out during summer. Without adequate insulation, heating and cooling systems must work harder, increasing energy consumption and fuel bills. According to the Energy Saving Trust, up to 25% of heat loss escapes through uninsulated walls and roofs. That’s a lot of wasted energy – energy you’ve paid for.

Reducing energy wastage is easy – add insulation. The principle is simple: insulation reduces the rate at which heat is lost through building elements. The better the insulation, the slower the heat escapes. And because heating systems don’t have to work as hard, you’ll not just save money – you’ll extend the life of your heating too.

But, insulating your home isn’t just good for your bank balance – it’s good for the planet too. By reducing energy consumption, your home will generate less carbon.

According to the UK’s Climate Change Committee, energy use in buildings accounts for around 17% of the UK’s total emissions and improving insulation is one of the most effective ways to meet net zero targets. And with lots of sustainable eco insulation products available, your choice of insulation can also help reduce the environmental impact of how it's made.

Best ways to insulate your home

1. Choose the best insulation materials

The choice of insulation materials is vast, each having their own pros and cons. Here’s how some of the most common materials compare:

• Mineral wool like this Rockwool from Wickes is dense, durable, and offers excellent fire resistance (withstands temperatures up to 1,000°C). Mineral wool insulation is also a good acoustic insulator. However, compared to fibreglass, it’s heavier, can be harder to work with, and requires relatively thick layers to achieve the required thermal performance. Its thermal conductivity typically ranges from 0.034 to 0.040 W/mK.
• Fibreglass (glass wool): Lightweight and affordable, fibreglass is a common choice for DIYers, especially for insulating lofts. It’s made from recycled glass and offers good thermal performance, typically around 0.044 W/mK, though higher-density batts can offer 0.034 W/mK. It’s less robust than mineral wool and prone to moisture absorption and sagging if not installed properly.
• PIR (Polyisocyanurate) boards: Manufactured as rigid insulation board, PIR is among the most thermally efficient products available, with conductivity as low as 0.022 W/mK. They’re ideal for insulating floors, walls and pitched roofs, where space is tight. PIR foam is closed cell, moisture resistant and durable. Unfortunately, it’s relatively expensive and difficult to install in irregular spaces.
• Polystyrene beads (EPS): Often used in retrofit cavity wall insulation, EPS beads are blown into the cavity, forming an insulation layer that resists moisture and mould. They’re suitable for walls exposed to driving rain, but come with higher costs and fire safety concerns, depending on the system.
• Cellulose Insulation is an eco-friendly material made from recycled paper treated with fire retardants. With a thermal conductivity of around 0.040 W/mK, it's typically blown into cavities and lofts and offers good performance, but, settles over time.
• Spray foam (Polyurethane): With excellent airtightness and good thermal resistance, spray foam sounds ideal. However, as a result of condensation problems it has become controversial due to potential impacts on mortgageability.
• Sheep’s wool: A natural insulation and sustainable choice that’s great at regulating moisture and providing decent thermal performance (around 0.035–0.040 W/mK). Sheep wool insulation like this Thermafleece on Amazon is safe to handle, biodegradable, and can absorb moisture, but watch out for bugs and high costs.

Each material offers its own balance of insulation cost, performance, and suitability. Rather than differentiating one product as better than another, it’s more about putting the right product in the right place.

For example, if you’re insulating a loft with ample space, fibreglass or mineral wool might be best. But for tight cavities or where thermal performance is critical, PIR boards will be the best option.

2. Add insulation in the right areas

• Loft insulation – Heat rises, and with around 25% heat loss, lofts are one of the most important areas to target. Laying rolls of mineral wool or fibreglass between and across ceiling joists is standard practice. For warm roof designs, rigid PIR boards can be installed above or below rafters but remember to maintain ventilation paths. A specialist alternative for insulating lofts is blown cellulose insulation. The objective is to distribute the loose fill material evenly to create a thick insulating layer.
• Wall insulation – Walls also have a potential for significant heat loss. Cavity wall insulation is built in during construction using rigid boards or mineral wool batts. For existing properties, blown-in insulation of either mineral wool or EPS beads are common. Solid walls can also be insulated internally with rigid boards or externally with insulated render systems subject to good quality design.
• Floor insulation – Ground floors can be insulated using rigid PIR or EPS boards laid over or below the slab of new builds. Suspended timber floors can have insulation fitted between the joists, though it’s essential to maintain ventilation to prevent rot.

3. Also consider where NOT to insulate

It's just as important to understand where to avoid when insulating your house. Areas in a home never to insulate include those with persistent damp or poor ventilation, and these shouldn’t be insulated without careful design.

Closing in damp with insulation will trap moisture, potentially causing rot, mould or damage to the insulation material. Watch out for thermal bridging – where gaps in insulation allow heat to bypass the insulated layer. This often occurs with bad fitting or around junctions such as window reveals, and can lead to mould growth.

4. Inject cavity wall insulation for a quick solution

Specialist contractors drill small holes in the mortar joints and blow in mineral wool, or polystyrene beads as cavity wall insulation. It’s relatively quick, but the wall must be in good condition, and materials should be chosen based on exposure risk.

5. Install rigid foam boards in walls and floors

Common in walls and floors, insulation boards are fixed directly to supporting timbers or blockwork or laid over floor slabs. They require precise fitting to prevent gaps and thermal bypass and may need joints taped to prevent interstitial condensation.

Shop rigid insulation board

6. Make sure you draughtproof too

You can have the best insulation in the world, but if gaps in windows, floors, or around pipes leak air, you’ll still lose heat. Draughtproofing seals uncontrolled air leakage, preventing cold air from getting in and warm air escaping.

Whilst this sounds contradictory, good insulation and airtightness must always be paired with controlled ventilation to avoid damp and poor indoor air quality.

Sealing around skirting boards and pipe penetrations can make a big difference especially when coupled with specialist MVHR systems to control the internal environment and recover warmth from unwanted stale air.

Shop draught excluders

FAQs

Can I install insulation myself?

Yes, especially when insulating lofts. But insulation systems that require specialist equipment or design are best left to professionals to avoid performance and damp issues.

Is cavity wall insulation always suitable?

No. If your home is in an exposed location, or the walls have particularly narrow cavities or are in poor condition, it may not be recommended. Always get a professional survey.

Will insulation reduce noise?

Absolutely. Materials like mineral wool are excellent at reducing airborne sound between rooms or from outside, but don’t forget, there may be alternative paths of noise transmission.

Is it worth insulating a suspended timber floor?

Yes, particularly if the floor is cold or draughty. Insulation can be fitted between joists but remember to maintain underfloor ventilation.

What’s the best insulation for a tight budget?

Fibreglass is one of the cheapest insulation materials. It’s widely available and performs well but isn’t necessarily suited to all situations.

Improving insulation is one of the most effective improvements you can make to your home. It saves money, enhances comfort, and helps reduce your environmental impact.

Whether you opt for fibreglass in your loft, rigid boards on the walls, or even eco-friendly cellulose, the key is to choose the right material for the job and to install it properly.

While insulating an extension you'll likely need to comply with building regulations. However, if you want to upgrade your entire home's energy efficiency you can also consider other measures such as switching out an old boiler for a more modern heating system like an air source heat pump.

Insulation remains one of the best ways of enhancing energy efficiency, reducing utility bills, and improving the year-round comfort in your home. And, whether you're renovating, extending or building a new home, when correctly specified, home insulation is going to save you money in the long run.

Insulation costs however do depend on the type of property you own, the area that needs insulating, and the material chosen.

In this guide to insulation costs, expert quantity surveyor, Tim Phillips, breaks down your options and costs for the four main areas of your home that need insulation: lofts, floors, cavity walls and external walls, so that you can calculate just how much to set aside for the future.

Factors influencing insulation costs

Understanding how to budget for your insulation costs requires taking a look at the different factors that can affect them. From the more obvious ones such as the type of insulation, through to more complex matters such as meeting Part L of the building regulations, here's what you will need to take into account.

New build vs retrofit

Although insulating an older home can have a positive impact, the downside is that installing insulation in an existing home can be much more problematic and costly.

In older properties, such as considering how to insulate a Victorian house, this may involve additional preparation such as removing old material, correcting any defects in the original structure, or accessing areas difficult to reach, such as narrow loft spaces.

Where plumbing or electrical services have been installed, it may also be necessary to adjust the insulation method accordingly, such as when adding internal wall insulation.

Most of the time, it is less complicated and more reasonably priced in new builds to install insulation as part of the building process. More materials can be used, and the insulation can be scheduled with other systems to ensure a hassle-free installation.

Size and type of insulation

The material type of insulation you need to install also varies in cost. Certain types are costlier because of the fact that they offer better performance regarding heat, or because of their close association with nature. As an example, rigid foam insulation boards are more costly compared to regular fibreglass rolls.

The thicker the insulation, the more your insulation costs will rise too. Thicker products consume more material, hence, the cost increases. However, a thicker product will have better thermal and acoustic performances and may save you more money in the long run.

Ease of access

Access to the location where insulation is needed can also impact your insulation costs. Installing loft insulation can be more labour-intensive and expensive if the loft area is hard to reach or if it does not have much headroom. Likewise, cavity wall installation costs might be higher than normal if the cavities are narrow or wonky.

For an existing home, insulating floors might also be a little challenging if there is not that much crawl space in your suspended timber floor, or if the concrete floor needs to be raised.

Labour costs

The cost of labour depends on a number of factors.

1. Complexity and location: In a retrofit installation, more specialised labour can be required, especially if existing homes have to be repaired or modified. Likewise where you live will result in generally higher labour rates for any work.

2. Size of the property: This automatically drives the cost up as larger homes will be more expensive to insulate simply because it will take more time and material to carry out the job.

Energy efficiency goals

Those homes that are looking to achieve strict energy-efficiency standards like Passivhaus for new builds, or Enerphit for retrofits ,will need specialised insulation. The inclusion of these standards into a design raises the cost significantly, especially for new builds.

Building regulations

Building regulations may require higher levels of insulation in areas of lower temperature, such as Scotland and Wales, which will increase your insulation costs. The same happens if the property needs to conform to a certain thermal and acoustic performance, which often increases the cost of new builds and retrofits alike.

Average insulation costs

All of the cost estimates that follow should be used as a general guide only, with considerable regional, size, and material differences to be expected.

However, having a general idea of installation cost estimates and possible savings will give you some proper ground on which to base your decisions regarding the type of insulation that best meets your needs and budget.

For an average three bedroomed semi-detached property, you can expect to pay the following average insulation costs:

Cost-effective loft insulation

Loft insulation maintains warmth during winter and keeps heat out during summer; this is simultaneously one of the most accessible and cost-effective methods to reduce heat loss. Heat rises, and as a result, up to 25% of a house's heat loss might be attributed to an inadequately insulated loft.

• Material cost: £5-£15 per square metre
• Installation cost: Approximately £300-£400 for a standard-sized loft in a semi-detached house
• Total cost: For a semi-detached house, the total would be in the range of £600-£1,000, but this may go up for thicker ones or the greener alternative
• Savings: Loft insulation can save from between £150 and £250 annually for heating for a semi-detached house.

Calculating internal wall insulation costs

It is possible to insulate solid walls significantly in order to reduce heat loss, since they tend to lose roughly about twice the amount of heat compared to cavity walls.

In such a situation, internal wall insulation significantly enhances thermal performance and is usually applied to internal solid walls. It is particularly suited for older solid-walled houses, as a lot of these were built pre-1920s, and looking at insulation for cavity wall construction is not an option. It can also be a good option for houses undergoing extensive interior renovations.

The main choices available to you are insulating internal walls with plasterboards comprising insulation adhered to the back. This is quick to install and less disruptive. Or, stud wall insulation in which a stud frame is erected against the wall and packed with insulation – most commonly mineral wool, but sometimes foam board. It provides superior insulation, though at a higher price while taking lesser inner space.

• Material cost: £20-£50 per square meter for insulated plasterboard or similar material
• Installation cost: £4,000-£7,000 for an entire house-inside wall insulation, usually for semi-detached houses
• Total cost: Overall, it costs between £7,000 and £10,000 for an average home
• Savings: The saving on the annual energy bills ranges from £200 to £450, depending on the size of the house and how much it has been insulated

Costs for insulating a solid external wall

External wall insulation includes the addition of an extra layer of insulation externally to the walls, which is then covered by a protective finish in an aesthetically acceptable finish.

This insulation reduces heat loss and weatherproofs the house. It is ideal for solid wall properties but works best in older homes where aesthetic or structural features allow for external modification. It is also recommended in cases when homes need an exterior facelift.

Insulation polystyrene boards are the lightest in weight and cost and will offer minimal disruption installation. Mineral wool boards on the other hand are mid-range and do offer good fire resistance and thermal performance. But, if your main goal is high energy efficiency, expect to pay extra for phenolic boards to meet your needs.

• Material cost: Material prices vary in the range of £50-£100 per m/2
• Installation cost: In a semi-detached house, the full installation price varies from £8,000 to £13,000, depending on the wall size and finishing
• Total cost: The estimated expenditure is roughly £10,000-£16,000 for an average semi-detached house
• Savings: EWI presents the possibility of saving between £250 and £450 per year, while savings are related to the size of a house and insulation levels

Working out cavity wall insulation costs

Most houses built after the 1920s have cavity walls, meaning there is a gap or cavity between an inner and an outer layer of brickwork. It is possible that filling this cavity with insulation is one of the most successful things you can do to avoid the loss of heat.

Suitable for houses built between the 1920s and 1980s, cavity walls that are not filled are ideal for upgrading.

However, make sure you avoid unnecessary costs by checking whether you're in an area where your cavity shouldn't be retro-filled due to the amount of wet weather it receives. Wales, Scotland and the West coast of England are a no-go.

• Material costs: £5-£20 per m2
• Installation costs: The installation price ranges between £800 and £2,750 for an average retrofit of a semi-detached home
• Total cost: Generally, falls between £1,600-£3,500 for most semi-detached properties
  Savings: Around £100-£250 on the annual energy bill is possible.

Budgeting for floor insulation

Adding floor insulation is very effective on ground floors, especially in unheated areas or in houses with suspended floors. It inhibits heat loss through the floor so that the ground floor areas feel warmer and more pleasant.

It can again be particularly useful for older properties where the floors may be quite draughty. Insulating suspended floors and insulating concrete floors are both achievable, and are good options for those renovating or extending a property.

• Material costs: The prices for materials start at £10-£20 per m2, using either rigid foam boards or their eco-friendlier counterparts
• Installation costs: Prices vary between £1,000 and £3,500, depending on the property size and its access points
• Total costs: Generally, it costs between £1,200 and £5,500 for an average house
• Savings: Potential to save £40-£100 per year on heating bills, although again it depends upon the property and the amount of insulation applied

Obtaining accurate quotes for your insulation costs

Like any element of work, it is worth getting at least four quotations for the different insulation projects, so you will be in a better position to compare costs and ensure that you are not charged an unfair price.

For best value against the money invested, comparison of quotations needs to be done by homeowners based on a number of key elements. Some of the most important factors to consider include:

• Insulation thickness – The performances of the insulation layer can be bound by its thickness regarding thermal and acoustic insulation. Compare how each quotation stacks up against one another for insulation thickness and their effectiveness in meeting your energy-saving goals. Check the 'U' value of the proposed insulation and ask for a thermal desk study to see what the finished thermal efficiency of the wall will be for differing options
• Installation technique – Note the recommended installation method for each quote provided, especially if your job is a retrofit. Find trustworthy insulation installers who can provide references for previous insulation installations. If it's a new build, then your bricklayer will be fitting the cavity wall insulation as the walls are built, or it may already have some insulation in situ if you're using MMOC (Modern Methods of Construction), i.e., structural insulated panels (SIPs), timber frame or insulated concrete formwork (ICF)
• Energy efficiency gains – With each insulation method, determine any potential energy gains that could be associated. Some estimates may give rough projections of future energy savings, which may be used to justify the upfront cost

Money-saving opportunities

Several insulation projects, due to their simple nature, are likely to attract some kind of government subsidy, incentive, or energy-efficiency drive to upgrade old housing stock.

Availability of such programs can lower the initial costs of retrofits so it’s certainly worth looking into the financial opportunities and grants the government makes available for energy-efficiency improvements. Incentives like these can vastly bring down the overall cost of installations, making them more accessible.

The easiest and quickest route to application is the government’s online eligibility checker. You will subsequently be asked about your address, council tax band and energy supplier, whether you are a landlord, renter or homeowner. Homeowners should investigate all avenues of funding and qualifying criteria before embarking on an insulation project. Moreover, you secure multiple quotations and work with accredited installers so that you maximise any subsidy or financing.

Money-saving options available include:

• ECO 4 (Energy Company Obligation 4): This is an ongoing government scheme whereby larger energy firms are required to fund home energy-efficiency improvements. Under ECO 4, your home might qualify for free installation, or at least highly subsidised external and internal wall installation, particularly for low-income and/or those in receipt of certain benefits
• Great British Insulation Scheme: A government scheme to help British homes be more energy-efficient. The scheme targets the least energy-efficient houses in the nation and is looked after by Ofgem, which aims at easing fuel poverty and reducing energy costs for households in general
• Local authorities: They often make funds or grants available to facilitate energy-efficient improvements, which are going to be the installation of external and internal wall insulation through the ECO Flex and LA Flex schemes. Homeowners should check with their council's website or make contact directly as to whether a grant is available and what the eligibility criteria are, since these schemes vary by area

As part of assessing your insulation costs, you maybe looking to understand whether you will get a return on your investment before you need to replace your insulation. Arm yourself with the facts by reading our guide to how long does insulation last and weigh up whether including some eco-insulation into the equation will give you the green home credentials you desire.

Living in a 1640s home has its benefits, but one of them is definitely not its heat.

It is a home that has failed its EPC rating due to it being so poorly insulated.

So when I got my hands on the Thermal Master P2 Pro, which you can buy online on Amazon, the world’s smallest thermal camera, I was genuinely curious to see how it would perform in a house that predates central heating by a few hundred years and see where my home needs better insulation.

Easy to use, right out of the box

First things first – this thing is tiny. It connects straight to your phone (I’m using an iPhone 12 max pro), and once I downloaded the Thermal P2 app within minutes I was scanning different areas of my home.

There’s no separate charging needed, which is a massive bonus. Just plug it in, open the app and off you go.

How I tested my home for heat loss

I started with the obvious culprits: the Edwardian-era windows.

As suspected, the edge of the windows lit up like a bonfire on the thermal infrared heating display – deep reds and oranges showed exactly where heat was pouring out while cooler greens and blues showed where everything was working as it should. No surprises there, but it’s great having visual confirmation when deciding whether to install double glazing!

Even the conservatory, a much newer feature, was shown to be leaking heat, revealing many ways how I can insulate my home better.

Next, I checked the internal walls and newer installations like the modern front and back doors.

The newer doors were shown to be impressively efficient, staying close to the house’s internal temp of 21°C, showing very little leakage.

The P2 Pro let me toggle between Celsius and Fahrenheit easily. However, what impressed me most was how sensitive it was – the device can detect temperature differences as small as 0.04°C, and the 15x zoom meant I could hone in on very specific areas, like door seals and corners of window panes and take almost immediate temperature readings.

12 different colour palettes & numerous features

With 12 colour palettes to choose from and the ability to adjust emissivity, I found it easy to customise the display for different materials – stone, wood, metal, glass – all of which exist in glorious chaos in my home.

There’s even a DIY colour bar where you can set thresholds manually and swipe to highlight problem areas – handy for creating professional-style inspection reports, which the app generates on the fly.

If you want to identify certain points in your home you can click the 'point' feature to take readings of individual spots, or draw a line using the 'line' feature, like I did on my windows, to compare temperatures, or even use the 'frame' feature to draw a block to see how much heat is being lost in a larger area of your home.

Battery & performance

I was concerned it might drain my phone, but with such low power consumption (just 0.33W), I got two hours of inspection time without any issues, despite my phone being on less than 30% battery.

The 256×192 IR resolution is sharp, and the smart algorithm bumps it up visually to 512×384 for even clearer images.

You can also store all of your images on the app in a gallery to keep track of all of your house and where poor insulation is a problem.

Is it worth it?

The Thermal Master P2 Pro is an absolute gem for any homeowner, especially those of us living in Britain’s beautifully drafty older homes.

Whether you're chasing down draughts in a 17th-century wall or checking modern fittings for leaks, this tool is a game-changer.

At £280-ish ($349), it’s not exactly pocket change, but for what you get – including the portability, accuracy, and all the pro features packed into something the size of a biscuit – it’s well worth the investment.

If you’re even remotely into DIY, home maintenance, or just curious about where your heating bill is going, this thermal camera will quickly become your favourite gadget.

Shop the Thermal Master P2 Pro

Looking into insulating a garage conversion needs to be top of your to-do list if you are considering turning this often wasted room into habitable living space.

If you are looking for ways to add space and value to your home without building a full-blown extension, a garage conversion could be the perfect way to achieve this. That said, unless you carry out the project carefully, you could be left with a space that isn't fit for purpose.

Here, we explain the steps you need to take when it comes to insulating a garage conversion to turn it into a comfortable room that you can't wait to spend time in.

What type of insulation is best for a garage conversion?

If your garage conversion ideas are for a habitable space, the walls, floor and roof all need to be insulated. The best and easiest way to insulate all of these tends to be with rigid board insulation.

"We use 100mm Kingspan insulation in both the walls and floors, and 120mm Kingspan in the roof space," picks up Jim Allsop, director of Convert Your Garage. "Kingspan is a high-performance rigid insulation board known for its excellent thermal properties, making it ideal for garage conversions where warmth and energy performance are key."

Shop rigid insulation, studwork and tools

What is the best way of insulating garage conversion walls?

"As garages were originally intended as unheated spaces, many feature solid wall constructions," begins Matthew Evans, director of technical and regulatory affairs GB at Kingspan Insulation UK. "These allow high levels of heat loss and will need to be properly insulated if you intend to convert the room into a liveable space."

When it comes insulating a wall, you have two options: external wall insulation, or internal. The advantage of external systems is that they take up no valuable space inside, plus they are less likely to suffer from any thermal bridges.

External wall insulation tends to take the form of boards that are mechanically fixed to the wall before being clad or rendered.

If you are keen to retain the external appearance of your garage or if space is restricted around it, an internal system might be better. They are also easier to fit on a DIY basis.

"The simplest way to add insulation to the walls is with insulated plasterboard fitted to timber battens above the damp proof course," explains Paula Higgins, Chief Executive of HomeOwners Alliance.

"Our typical approach involves timber framing the garage walls with 4"x2" timbers, before carefully housing rigid board insulation between the studs," explains Jim Allsop. "This method ensures a tight fit, reduces thermal bridging and helps achieve a smooth internal finish ready for plasterboarding."

If your garage happens to have been built after around 1920 and is attached to your house, you might find it has cavity walls, in which case, insulation can be in the form of rigid boards, mineral wool or injectable insulation.

Matthew Evans has some words of wisdom to take note of before deciding on an insulation route.

"Before ordering any insulation, it is important to assess the building for any defects which might cause issues," says Matthew. "These include any clear signs of damp or moisture on the walls or issues which could lead to this, including missing pointing, damaged gutters or an absent damp proof course. These must all be carefully assessed before you start any work."

How do you insulate a garage conversion floor?

You will also need to add look into insulating floors in your garage if you want to use it as habitable space.

"When garages are originally planned and built, their hard concrete floors are supposed to weather the wear and tear of DIY, leaking cars and storage units," picks up Matthew Evans. "With some careful preparation and the right solutions, however, it is relatively simple to transform these into a well-insulated floor space for a living area."

"Garage floors are usually lower than the floor in the main house so you should be able to add a damp-proof membrane, insulation and a new screed plus floor covering and end up level with the rest of the house," explains Paula Higgins.

Most garage floors are solid concrete and it is simple to lay rigid insulation board on top of this, over your damp-proof membrane and beneath your screed. If you are adding underfloor heating too, make sure you take final floor levels into consideration.

"Start by laying a damp proof membrane (at least 300 microns thick) above the concrete deck," advises Matthew Evans, who goes on to recommend a rigid board insulation such as Kooltherm K103 Floorboard be installed.

"The boards should be fitted in a break-bonded pattern and tightly butted together," continues Matthew." A 20 mm thickness of Kooltherm K103 should also be fitted vertically around the edge of the floor to the expected height of the floor screed which will be laid above the insulation. This is to help prevent heat loss from thermal bridging at this junction."

If the floor level of your garage is considerably lower than that in your house, you might like to consider building an insulated suspended timber floor.

Do garage conversion roofs need insulating?

The final area to turn your attention to when insulating a garage conversion is the roof. This is done in much the same way as if you were insulating the roof of a house.

"Roofs can account for a lot of heat loss, so if you’re converting your garage, it’s important to ensure it is well insulated," explains Matthew Evans. "In most cases, garage roofs use a flat roof construction.

"When insulating a garage roof, we would always recommend fitting the insulation above the roof deck," continues Matthew. "This is known as a 'warm roof construction.' The advantage of this approach is that it reduces the risk of moisture condensing on the cold building structure and leading to damp issues."

Insulation can be fitted between the joists of both flat and pitched roofs – with rigid boards being the most suitable option for both.

In terms of how much insulation to fit into your roof, you need to be aware of U-values.

"Most garage conversions are classed as an extension of an existing building in the Building Regulations," explains Matthew. "This means the roof will need to achieve a minimum level of thermal performance (a U-value)."

In England this 0.15W/m²K, 0.13W/m²K for Wales and 0.12W/m²K.

"Start by fitting a vapour control layer over the deck, ensuring the layers overlap each other by at least 150 mm and are turned up at the edge of the roof to the height required for your waterproofing system (this should be included within the manufacturer's guidance)," advises Matthew. "A rigid insulation board such as Thermaroof TR26 can then be fitted above the membrane with suitable fixings. The boards should be lightly butted and break-bonded. A 25 mm thickness of the insulation needs to be fitted around the perimeter of the roof to prevent thermal bridges.

"Any rooflights or ventilator kerbs should also be insulated to the same level," continues Matthew. "The roof membrane can then be fitted following manufacturer guidance for the system."

What are the building regulations for garage conversion insulation?

Insulating a garage conversion falls under Approved Document L of the Building Regulations.

"The guidance provides U-values, which are a measure of how thermally effective a thermal element (the roof, walls or floor) is," explains Matthew Evans.

"In England and Wales, where a garage is being converted to become part of the heated building, then the walls must meet the requirements for adding and replacing thermal elements, or the requirements for renovating elements (depending on the work being carried out)," continues Matthew.

FAQs

Does the wall between the garage and existing house need insulating?

The good news here is that you won't need to insulate this wall.

"Since there is no longer such a drastic change in temperature between the cold garage and the warm house, with the aim to keep both spaces comfortably warm, there is no need to insulate the wall between your house and the new garage conversion," confirms Matthew Evans.

While not all garages feature flat roofs, most seem to. If your own garage is one of them, be sure to look into how to insulate a flat roof to ensure you know what you are dealing with.

If you’re a self builder, installing cavity wall insulation (CWI) is crucial to keeping your home warm and energy efficient. Get it wrong and the issues can be costly to fix and will negatively affect your home's efficiency – so it's important to get it right from the outset of your build.

But what's the best practice for getting the job done – both in new homes and when considering your options for a home renovation?

In this guide we explain how much insulation you will need, how to install it correctly and what you can expect to pay.

The importance of correct installation

"There is a strong argument that a cavity wall without insulation is only half a wall. The function of a wall is to keep the weather out, which does not just mean the rain, but heat as well," says sustainable building expert, Tim Pullen. "An increasingly important function of insulating a wall is to keep the heat on the right side: inside in winter and outside in summer. Which means installing insulation, and in the right way to avoid cavity wall insulation problems."

Getting cavity wall insulation wrong can be a disaster and expensive – as the sheer position of being inside a wall can make it very difficult to access. However, on the plus side, there are only two main fundamental issues to getting this process right:

1. Using the right amount and best product: The majority of expense is in the work involved in installing it, not in the types of insulation used. The current requirement is to achieve a U value of not more than 0.18W/m2, but it’s possible that this drop to 0.15W/m2. Given the cost of energy and the whole CO2 issue, it would be wise to aim for that lower figure. However, even a U value of 0.18W/m2 figure will need 100mm of rigid foam insulation (Xtratherm, Celotex CW4000 or similar) or 170mm of mineral wool.

2. Correct installation: Install it with the same care and attention to detail that would be lavished on fitting a kitchen. Bad installation is where problems will occur – be that damp penetration or loss of thermal efficiency.

Installing cavity wall insulation in masonry walls

To achieve the best results when installing cavity wall insulation as part of the process of building with masonry, it's crucial to start with high-quality insulation that's free from damage and has been stored correctly on-site. Insulation boards that get wet or damaged won't work effectively.

One challenge is that insulation is typically added to the wall cavity during construction, which can expose it to moisture overnight. It's important to ensure the top of the wall is well weatherproofed as construction progresses to maintain insulation performance.

When using wall ties, plastic ones are ideal for preventing heat loss, but if not available, some bricklayers may opt for steel ties, which should not penetrate the inner wall by more than 25mm.

Then, in order to obtain a well insulated and watertight wall, self builders need to install 100mm of insulation and completely fill the cavity to maximise thermal performance and minimise the wall thickness.

Mark Stevenson, one of Homebuilding & Renovating's self build expert recommends the following tips:

• If using rigid boards, build the inner blockwork first to hold the boards in place
• For mineral wool, build the external brickwork first to keep it clean and reduce moisture risks
• Insulation boards must be fitted tight, with no air gaps and adequately supported with wall ties and retaining discs
• If necessary, joints should be taped to ensure gaps are closed
• Remove excess mortar from wall ties and joints to prevent moisture penetration
• Use foil-faced insulation boards for fully filled cavities to block moisture
• Ensure cavity closers are also insulated to eliminate thermal bridges

In addition, Tim Pullen states it's essential to, "ensure all mortar joints are filled, the bottom of the cavity is kept free of mortar droppings and all excess mortar is removed from both outer and inner skins.

"Each row of insulation boards also needs to be supported with at least two wall ties, the insulation is tight and in flush contact with the inner leaf of the wall and where possible, cuts to insulation boards to accept wall ties should be avoided as much as possible," he adds. "Where cuts are made, the gap should be filled with insulation off-cuts."

Installing cavity wall insulation in timber frames

"When dealing with timber frame walls, you don't have to worry about fitting insulation tightly to an inner layer because the timber frame serves as that layer," says Tim Pullen.

"However, choosing the right insulation type and thickness can be a challenge. Typically, to achieve a U-value of 0.18W/m2, you'll need 140mm of rigid foam insulation, which is a standard stud thickness for timber frame construction. Thicker walls are possible but tend to be customised, especially if you're using flexible or semi-rigid insulation materials like Rockwool, wood fibre insulation, hemp or sheep wool."

Tim explains how the main issue with rigid insulation is that it's harder to install precisely because it needs to be cut to size, often leading to small gaps between the insulation and timber studs, reducing thermal performance. Semi-rigid insulation is a solution since it's cut slightly larger to ensure a snug fit, eliminating gaps and slumping, a problem that can occur with flexible insulation.

"Achieving a target U value of 0.18W/m2 may require 190mm of semi-rigid insulation, which exceeds the standard timber frame thickness," he adds. "One approach is to install 140mm of semi-rigid insulation within the stud wall and add another 50mm layer of rigid insulation on the outside of the timber frame (using rigid foam or wood fiber) with a brick, timber, or render weatherproof outer layer. This combination meets the U-value requirement and offers excellent thermal efficiency."

Retrofitting cavity wall insulation

Internal wall insulation in a renovation can be tricky because different projects vary. However, in all instances the first step is to determine if your walls have a cavity and whether there's any existing insulation.

If your house was built after 1920, it's likely to have a cavity, but it's best to consult a reputable installer who can use a borescope to inspect the wall. They will drill a small hole in the outer layer, insert a tiny camera, and visually assess the cavity's condition (if present).

This inspection also checks for any debris, like mortar droppings on cavity ties, and confirms if there's existing insulation. If your wall has a clean and empty cavity, you can proceed with injected insulation, which performs similarly to rigid foam. The use of injected insulation is dependent on the width of the cavity – likely to be 50mm – but it’s better than nothing.

Consider using a thermal imaging camera to ensure the insulation fills the entire cavity properly. "In some cases, incomplete insulation may not become apparent until later," warns Tim Pullen, "leading to issues like black mould forming around windows two years down the line."

Costs of installing cavity wall insulation

With a new build there is no extra cost to insulating a wall, as insulation must be installed as part of the overall build in order for your property to comply with Building Regulations. But when it comes to how to insulate an old home the costs can vary depending on the project.

The Energy Saving Trust tells us that cavity wall insulation can save up to around £370 a year on your energy costs and that injecting insulation to an existing wall can vary in price and can vary from around £1000 for a mid-floor flat up to £4000 for a detached home.

When it comes to making sure your cavity wall insulation is professionally installed and cost-effective is understanding that, "all cavity wall insulation must meet strict quality standards. Installers should be certified by organisations like the Cavity Insulation Guarantee Agency (CIGA)," says Mark Stevenson. "Materials must also have the necessary certifications to ensure they are fit for purpose."

FAQs

How do I avoid thermal bridges?

"A thermal bridge is a weak spot in the insulation. Essentially, it’s where a line can be drawn from the inside to the outside of a building without passing through a full thickness of insulation – or where there are gaps in the insulation," explains Tim Pullen. "It’s also where highly conductive materials (steel wall ties, steel lintels, etc) penetrate from the inside of the house to the outer leaf." For more information, head to our guide on what is a thermal bridge.

The Building Research Establishment (BRE) have stated that even a well-insulated house’s thermal bridges can account for 30% of heat loss. Such a problem can be solved with good design and attention to detail during construction and ensuring that insulation in the floor, walls and loft overlap sufficiently.

Installing cavity wall insulation is a job you really need to get right both in new and old homes. But, it's also about making sure all parts of the job are done well, so make sure you avoid this cavity wall closer mistake as well, in order to avoid any problems in the future.

A groundbreaking new mortar mix developed by scientists from Newcastle University could transform how homes are built.

By swapping out traditional sand for recycled plastic and high-tech aerogels, researchers have created a lighter, eco insulation material that reduces heat loss by up to 55%.

This innovation could mean lower energy bills, less plastic waste and a major step forward for sustainable construction.

Plastic bottles turned into high-tech building material

Instead of using conventional sand, scientists integrated shredded PET plastic from recycled bottles and combined it with silica aerogel – a material famous for its ultra-lightweight and insulating properties, even used in space technology.

This blend not only improves insulation but also makes the mortar significantly lighter while maintaining the strength needed for construction.

Publishing their results in Construction and Building Materials, the team confirmed that the mortar meets international construction standards, making it a realistic option for builders looking to improve energy efficiency in new homes.

Homes stay warmer while fighting plastic pollution

This innovative mortar could help solve two major global problems at once – energy price rises and plastic waste.

Traditional mortar allows heat to escape through gaps between bricks, but the new formula locks in warmth, potentially lowering heating bills.

At the same time, it provides a smart way to repurpose plastic waste, reducing the amount that ends up in landfills or oceans. Professor Lidija Šiller, one of the lead researchers, sees a huge opportunity: “Wouldn’t it be incredible if we could cut heating bills for new homes while tackling the plastic waste crisis at the same time? Our study shows it’s possible.”

Testing in real homes

Now that the formula has been proven in the lab, the research team is eager to take it to the next level. They are looking for industry partners to help bring this mortar to real construction projects and test its long-term benefits in actual homes.

PhD researcher Kaniaw Marof, lead author of the study, believes this could be a game-changer: “Improving insulation in masonry buildings is one of the biggest challenges in construction. Our mortar not only reduces heat loss but also makes use of materials that would otherwise go to waste.”

With growing demand for greener homes, this innovation could become a key player in the future of energy-efficient construction – where homes are not only built stronger but also smarter.

In an effort to accelerate the UK’s transition to a more energy-efficient housing market, new regulations will require all rental properties to achieve a minimum Energy Performance Certificate (EPC) rating of C by 2030.

While these regulations are a step forward in making homes more sustainable, they also present significant challenges for landlords and homeowners, from the financial costs to questions about the accuracy of EPC assessments.

We take a look at these challenges and what homeowners and landlords need to be aware of.

The scale of the challenge

The challenge of reaching EPC C is vast. According to data from epIMS, an energy efficiency platform for landlords, over a third (33.8%) of all homes listed for sale in Britain fall below the required EPC C standard.

This figure is even higher in parts of the UK - around 50.1% of homes in Wales and 45.7% in Scotland are not up to scratch. England fares somewhat better, but still, 33.2% of homes would fail to meet the new EPC regulations.

In cities like Bradford, over 46% of properties fall below the required standard, with other cities such as Edinburgh (39.6%) and Brighton (39.4%) not far behind. Even London, where energy-efficient properties are more common, still sees almost a quarter (23.5%) of homes rated D or lower.

This stark reality highlights the huge scale of the task ahead, with millions of properties needing upgrades to meet the EPC C target.

The cost implications for landlords and homeowners

One of the biggest concerns with the new EPC requirements is the cost. Landlords, in particular, face substantial financial pressure to upgrade their properties.

Research suggests that the average cost of bringing a property up to EPC C standard is around £8,000. For many landlords, this represents a significant outlay, especially after facing multiple regulatory changes in recent years.

Craig Cooper, COO of epIMS, expressed his concerns: "Landlords have already faced numerous legislative changes that have affected their financial returns. The requirement to meet an EPC C rating is another significant hurdle.

"While a greener rental sector is a positive development, the government’s fabric-first approach may not always be the most cost-effective for landlords. Alternative solutions, such as installing solar PV panels, could be a more affordable way to achieve the necessary improvements without incurring excessive costs."

Karl Bantleman, Managing Director of building suppliers Direct365, highlighted practical changes that can be made at a lower cost: "Small upgrades like switching to LED lighting, improving insulation, and installing smart thermostats can make a noticeable difference in EPC ratings. Larger changes, such as replacing an old boiler, will require a bigger investment but can significantly increase both energy efficiency and property value in the long term."

Is the EPC system fit for purpose?

While EPCs are intended to provide a snapshot of a property’s energy efficiency, questions about their accuracy and fairness are raising concerns.

Consumer watchdog Which? has called for an overhaul of the EPC system, citing inconsistencies in assessments and outdated evaluation methods.

Research reveals that only 36% of UK homeowners are aware of their property’s EPC rating, and only 29% have reviewed the recommendations for improving it. Which? argues that EPCs should be updated to reflect real-world energy use and incorporate modern, low-carbon heating solutions, instead of relying on assessment methods that may not consider the full scope of energy-saving measures.

Tim Pullen, an energy expert at Homebuilding & Renovating, criticised the system’s outdated approach: "The software used to generate EPCs is outdated and fails to account for new technologies accurately. The system needs an overhaul to provide homeowners with a more reliable and realistic measure of their property’s energy efficiency."

Real-life examples of EPC ratings

A real-life case shared by Homebuilding & Renovating illustrates the challenges in accurately assessing a home’s energy performance.

A couple who had invested heavily in their eco-friendly home – installing high levels of insulation and an air source heat pump – saw their EPC rating drop from a C to a D. The downgrade occurred because the assessor was unable to account for the unseen energy-saving measures they had installed.

David Hilton, a heating expert, commented on this: "It’s absurd that a home’s energy efficiency rating depends on what an assessor can visually confirm, rather than taking into account documented energy-saving features. This undermines efforts to improve sustainability in the housing sector."

How homeowners and landlords can improve their EPC rating

To help homeowners and landlords meet the new EPC requirements, the government has introduced several support measures, including grants and incentives.

For example, the Boiler Upgrade Scheme offers up to £7,500 for the installation of heat pumps, and further financial assistance may be made available as the 2030 deadline approaches.

Nic Gillanders, CEO of SCIS, emphasised the need for collaboration: "Improving energy efficiency is critical for reducing national grid strain and fighting climate change. If implemented correctly, EPC regulations could be a game-changer for sustainability, but only if landlords receive the right support."

With the 2030 deadline looming, landlords should start planning upgrades now to avoid penalties. Suggestions for improving EPC ratings include improving insulation, upgrading heating systems, replacing old boilers, and considering the installation of renewable energy sources like solar panels.

Additionally, homeowners can benefit from energy audits, which can help pinpoint areas for improvement and ensure that the right measures are taken.

While these changes come with a cost, the long-term benefits of a greener property – including reduced energy bills and increased property value - are significant. Moreover, the move towards higher energy efficiency aligns with the UK’s broader goals of tackling climate change and reducing carbon emissions.

You might have heard that spray foam insulation in a property can affect your chances of getting a mortgage or invalidate your home insurance, but is this true?

Spray foam insulation has gained popularity as an energy-efficient solution for homeowners, but numerous reports have come out that it can have significant implications for mortgages and home insurance.

We asked the largest mortgage lenders and home insurance providers in the UK about their stance on spray foam insulation and any tips they have for homeowners thinking about installing it.

Potential negative effects of spray foam insulation on homes

While spray foam insulation can improve a home's energy efficiency, it also comes with potential downsides that may affect a property’s value and structural integrity.

The Royal Institution of Chartered Surveyors (RICS) warns that "the presence of spray foam may affect a surveyor’s valuation of a property, especially if it has been applied incorrectly."

One of the key concerns is that spray foam creates an airtight seal, which can trap moisture and lead to condensation. Over time, this can cause timber supports in the roof to rot, compromising the structure.

Another issue is structural stress. Closed-cell spray foam sets rigidly and can add weight and pressure to roof supports, sometimes leading to distortion or even damage.

What mortgage providers say about spray foam insulation

Many mortgage providers are cautious about lending on homes with spray foam insulation, particularly for older properties. Here’s what some major lenders have said when we spoke to them:

• Santander: "The presence of spray foam does not prevent a Santander mortgage application, with properties assessed on a case-by-case basis. A surveyor may need further information, such as a Structural Engineer’s report, to fully assess the property as part of the mortgage application process."
• HSBC: "There are risks attached to the use of spray foam insulation, which include the potential for moisture to be trapped against roof timbers and for significant structural defects to remain concealed. Spray foam to roof spaces is unacceptable for any listed buildings, and we will not provide lending against them. For other properties, it may be acceptable if a suitable specialist report (in accordance with PCA protocols) and a warranty is provided."
• Lloyds: "We do not have a ban or block to lending on homes with spray foam insulation; we look at each case on its own merits based on the surveyor’s report."
• Nationwide: "We will lend on properties with spray foam insulation. However, in cases where the installation doesn’t comply with manufacturer’s recommendations, there is a risk of damage to the roof structure. As such, where a valuer sees evidence of spray foam, we require evidence it has been installed correctly before lending."

A BBC report from last November found that some institutions, including TSB Bank, Skipton Building Society, Co-operative Bank, Principality and Aviva refuse to lend on properties with spray foam insulation in the roof space.

What insurance providers say about spray foam insulation

Home insurance providers also take varied approaches to spray foam insulation.

A spokesperson for The AA stated: "We don’t ask about insulation type when quoting policies, so there’s no risk acceptance based on spray foam alone. Similarly, we haven’t declined any claims due to the insured installing spray foam insulation."

However, they advised that homeowners should seek specialist advice before installation to ensure it is appropriate for their property and won’t create future issues whilst warning about rogue spray foam operators.

Some insurers, such as Hastings Direct and Markerstudy Insurance Services, declined to comment on their stance.

If you are considering spray foam insulation, consult with a specialist to assess what type of roof insulation your home’s needs.

Before installation, check with mortgage providers to ensure it won’t affect your ability to secure financing or remortgage your home in the future.

Also, review your home insurance policy to confirm that spray foam insulation won’t impact coverage or claim eligibility. If purchasing a home with existing spray foam insulation, request surveyor and specialist reports to identify potential structural issues.

Understanding these factors can help homeowners make informed decisions about spray foam insulation and avoid potential financial or structural complications in the future.

As a building material, insulation is incredibly important as it sets the thermal performance of your home. Home insulation is essential for energy efficiency, maintaining internal comfort, and keeping energy bills low.

However, like all materials, insulation has a lifespan, and over time, it undergoes an aging process that can reduce its effectiveness.

In this article, expert builder, Mark Stevenson reveals how different types of insulation age, the factors that contribute to their degradation, and how you can maintain them to keep your home warm and energy bills affordable.

Can you increase how long insulation lasts?

The longevity of insulation depends on several factors, including the material’s inherent properties, environmental conditions, and how well it’s installed.

The most common types of insulation include Polyisocyanurate (PIR), mineral wool (stone wool and glass wool) and fibreglass quilts. Each one has their own unique make-up that plays a part in how well it ages.

Whether you’re choosing PIR for its thermal resistance, mineral wool for its fireproofing qualities, or fibreglass insulation for acoustic properties, understanding how the performance of these insulation materials are affected will help to maintain their performance and maximise their longevity.

Whilst studies have proven that the aging of insulation materials is inevitable, the rate at which it happens can be slowed with proper installation, moisture control, and regular maintenance. By taking care to follow manufacturers' installation and maintenance guidelines, self builders can ensure that the insulation of their homes will control energy costs and maintain comfort levels for at least the time they’ll live in their home, and most probably will last the lifetime of the building.

How long each type lasts

PIR insulation

PIR insulation is a popular choice for self builders as it's one of the most energy efficient insulation products available. PIR insulation is a foam that is formed with closed cells filled with low-conductivity blowing agents. These agents help to keep the material’s thermal performance high.

However, over time, these blowing agents begin to diffuse out of the cells and are replaced by gases from the surrounding atmosphere. Studies have established that as the low conductivity blowing agent is replaced, the insulation becomes less efficient as it ages.

This process usually starts after 5 to 10 years and very warm environments can speed up the process, causing the insulation to lose its thermal resistance, making it less effective at keeping buildings insulated over time.

Although PIR is very durable and is resistant to moisture, if the insulation is allowed to get wet, its thermal resistance will be adversely affected. It's therefore essential that PIR insulation is installed correctly, and any leaks are rectified. Vapour control layers (VCL’s) should also be properly installed and designers should always complete a condensation risks analysis to ensure construction details are effective.

Mineral wool insulation (stone wool and glass wool)

Mineral wool, which includes both stone wool and glass wool, is well-known for its fire resistance and durability. These materials are also less prone to aging compared to other types of insulation.

Stone wool is made from volcanic rock and slag and has a high resistance to moisture and high temperatures, which makes it incredibly durable. Manufacturers of stone wool claim that it can last at least 65 years and this has been supported by studies which also found that insulation removed from a 65 year old building, still offered a good level of thermal performance.

Glass wool is made from recycled glass, and while it shares many attributes with stone wool, its main weakness is exposure to moisture. Prolonged exposure to moisture can cause the fibres to compress and lose their ability to trap air, reducing its insulating properties.

In addition, repeated heating and cooling cycles can cause stress within the fibres which leads to breakdown of the insulation. A recent study by the University of Cambridge found that after 25 years of thermal cycling, glass wool only degraded by about 2%, however, they also found that if moisture was not properly controlled, its lifespan would be significantly reduced.

Fibreglass insulation

Fiberglass is made of woven glass fibres, and is a very cost effective insulation often used to insulate lofts. It offers a good thermal resistance as well as soundproofing qualities, but like any insulation material, it is prone to aging – particularly where there’s moisture and compression. Studies have shown that when properly installed, fibreglass insulation will retain about 95% of its thermal resistance for about about 40 years. This means that at some point over a building's life, the loft insulation may need to be topped up.

Moisture is one of the main causes of fibreglass degradation and when it gets wet –whether from leaks, condensation in a loft, or high humidity – it loses its ability to insulate. Studies have found that fibreglass insulation can lose up to 50% of its thermal resistance when exposed to moisture. Wet fibreglass can also become a breeding ground for mould, which not only affects the insulation’s performance but also the overall air quality in a building.

Fibreglass is prone to settling over time under its own weight and when not installed correctly. This compression, sometimes referred to as slump, prevents the insulation's ability to trap air and can lead to gaps and voids that affect the building's insulation performance.

Signs of ageing insulation

In most instances, there are some key common signs that identify potential ageing problems with your insulation.

• Visible damage: Discolouration, holes, tears, or sagging in the insulation material
• Increased energy bills: A rise in heating or cooling costs can indicate reduced insulation efficiency
• Drafts or temperature fluctuations: inconsistent temperatures or cold spots suggest that insulation is poorly performing
• Presence of stains, mould or mildew: Indicates moisture infiltration and compromised insulation
• Compacted or settled insulation: Loss of ‘fluffiness’ and thickness suggest that the fibres of quilt insulation has lost structure which will reduce its insulation effectiveness
• Pest infestations: Evidence of rodents or insects damaging insulation
• Physical damage: Crumbling, tearing, or brittleness and cracking of PIR insulation or peeling of insulation facings

Shop these insulation products

How to minimise your insulation ageing

While there are different methods recommended for each type of insulation, one of the most common causes of insulation degrading prematurely is moisture. Control this, and it's likely the lifespan of each type will improve.

Other measures specific to each type of insulation are as follows:

PIR insulation

Firstly, it’s important to acknowledge that as the aging effect of PIR insulation is well understood, its declared thermal resistance is adjusted to reflect the normal aging process. This means that the insulation is expected to perform better in the early years, but will decline to the declared performance over time.

To reduce the aging effects, correct product selection and proper installation is essential. For example, foil faced PIR insulation should be used in places where there’s a risk of moisture. The foil face seals the face of the board, which, along with adequate ventilation prevents moisture penetration and controls the aging process.

A correctly positioned vapour control barrier (VCL) will also help to control moisture penetration from the warm environment of your home. Manufacturers recommend that joints and cut edges of PIR should be sealed with foil tapes. In response to this, specialist products such as Gapotape have emerged, which ensure that the PIR board is sealed and tightly fitted, thereby eliminating unwanted moisture and air movement which would otherwise accelerate the aging process.

Mineral wool insulation

Once again, moisture control is the key to longevity and both products should be kept dry with appropriate measures to prevent moisture ingress from condensation or water leaks. It’s also a good idea to regularly check the insulation for any signs of settlement or moisture penetration.

Whilst mineral wool can withstand high temperatures, consistent exposure to extreme heat will cause problems, so keep an eye on any installations near high heat sources such as flues.

Fibreglass insulation

To extend the life of fibreglass insulation, proper installation is once again the key. Make sure the insulation is installed with no gaps and allow it to fill voids without compression. The insulation must be kept dry so address leaks quickly, and ensure there’s adequate ventilation to carry away unwanted moisture and condensation.

As with other types of insulation, the declared performance values of fibreglass insulation is often adjusted to account for potential performance loss due to compression. However, it is still a good idea to check for moisture, mould, or signs of vermin or compression. Replace any damaged areas and top up insulation that has slumped to maintain the required level of insulation.

For more information on insulating your home, follow our expert guide to external wall insulation and discover which types of acoustic insulation could suit a noisier home.

If you’re building a new home or extending an existing house and have done some research, you’ve probably realised that timber frame construction is a popular choice.

It’s energy-efficient, quick to build, and affordable, making it popular among self builders looking to cut energy bills and speed up their projects. With improvements in building regulations and tighter energy efficiency requirements, timber frame systems have also evolved a lot over the years.

Today, many timber frames are manufactured in factories to strict quality standards and come equipped with all the necessary insulation, airtightness membranes, and service zones. These are known as closed panel systems, and they’re a great choice because they offer reliable performance and third-party accreditations to ensure you meet all the necessary regulatory standards.

However, not every project can take advantage of closed panel systems. If you’re building an extension, particularly one where access is difficult, it might be more practical to build the frame piece by piece, or “stick by stick.”Or, perhaps you own an older timber frame in need of renovation. Either way, whether building from scratch or upgrading an existing frame, you’ll need to know how to insulate your timber frame walls effectively.

How to insulate a timber frame – why even non-closed panel systems are more energy efficient

A timber frame is essentially a structure made from softwood studs, typically about 38 x 140mm, with OSB/3 (Oriented Strand Board) attached to create a strong, load-bearing wall.

These days, thermal performance has become more advanced, and insulation products are used to eliminate heat loss by covering the timber structure either inside or outside the frame.

What’s great about timber frame systems over traditional build methods is that the spaces between the studs are perfect for fitting insulation, improving the wall’s thermal performance without adding unnecessary thickness.

What are the rules for insulating a timber frame

When insulating a new timber frame home or a timber frame extension, one of the main considerations is energy efficiency, as this directly impacts your energy bills, but it’s also essential it’s completed in line with the rules and regulations.

To ensure your home meets the Building Regulations, your insulation must provide the necessary level of thermal performance, commonly measured as a U-value. The U-value reflects how well a material prevents heat from escaping – the lower the U-value, the better the insulation. U values are calculated from the thickness of a building element and the level of thermal resistance the insulating materials provide.

For a timber frame wall, you’re aiming for a U-value of 0.18 W/m²K for extensions and upgrades to existing walls, and ideally something lower than 0.18 W/m²K for new builds – subject to passing the SAP calculations assessment.

How to choose the right insulation

When insulating a timber frame structure, there are several building elements relating to the external walls and roofs. There are several insulation options available, each with their own distinct features, benefits, and potential drawbacks.

While you need to choose the right type to hit a U value or thermal resistance, you’ll also need to think about sustainability, fire safety, durability, and how well the insulation manages moisture. You’ll also need to consider how easy the material is to install, especially if you’re doing the work yourself.

The most common insulation options include mineral wool, rigid foam boards, sheep’s wool, cellulose, and spray foam insulation. While the more detailed pros and cons of each type can be found in our guide to types of insulation, they are all suitable for timber frame structures, with each one offering varying degrees of suitability.

Insulating external walls

In timber frame walls, insulation is placed between the timber studs in the wall cavity. Mineral wool is a popular option because it’s affordable, fire-resistant, and provides good acoustic control. It’s also DIY-friendly. However, mineral wool has a lower thermal resistance, meaning thicker walls are needed to meet U-value requirements.

Rigid foam boards (e.g., PIR) deliver better thermal performance, but they’re trickier to install, especially with thicker boards. To avoid heat loss through air gaps, it’s crucial to cut the boards squarely and fit them tightly to the frame.

If sustainability is your priority, cellulose insulation is a great option but will need to be professionally installed using specialist equipment. Sheep’s wool insulation is an eco-friendly alternative, which is durable, easy to handle, and non-irritating. However, it’s more expensive and less thermally efficient than petrochemical-based options.

A key challenge with timber frame walls is thermal bridging. Heat loss occurs where the timber studs interrupt the insulation. This can be reduced by using rigid foam boards as an internal liner, creating a continuous thermal barrier over the entire frame. Provided you have at least some basic DIY skills, these liners and the necessary vapour control layers can be installed without too much trouble.

Insulating a timber roof

The type of roof insulation material used for a roof depends on whether it’s a warm roof or a cold roof.

Warm pitched roofs (common in rooms built into the roof space) are insulated over and between the rafters. Rigid foam boards are ideal because they provide excellent thermal performance while allowing ventilation gaps to be maintained. Given the height involved and skill needed to do a good job, installation is best left to the professionals.

Cold pitched roofs (usually in unheated lofts) are insulated at ceiling level, between and over the joists. Mineral wool is affordable, easy to install, and great for DIY, but a significant thickness is needed to meet regulations. Loft ventilation at the eaves is essential to prevent moisture build-up and condensation.

Avoid using spray foam insulation on cold roofs. While it expands to fit perfectly, its impermeable nature traps condensation, which can lead to structural damage over time.

Insulating the floor

Intermediate floor zones (between the ground and first floor) are often overlooked when it comes to thermal insulation. They need insulation primarily for soundproofing. Mineral wool is a good DIY solution, but it’s not thermally efficient at the floor perimeter. For better performance, use rigid foam boards like PIR to insulate floor edges, mirroring the approach used for walls.

In the end, the right insulation choice will depend on the specifics of your project, whether it’s a new self-build or a house renovation, and if you intend to DIY the installation. The perfect choice might be a hybrid of the insulation options so more of the boxes get ticked.

However, whichever option you go for, it's worth remembering that insulation is a highly technical product, and is only one part of the building system. The installation should therefore be designed and checked to make sure it's technically compliant and appropriate for the circumstances.

When deciding between mineral wool and fibreglass insulation, the choice can be tricky, as on initial inspection both can look similar.

However, while both are popular for home insulation, they offer different advantages depending on your project’s needs. Whether you’re insulating a loft, walls or floors, understanding their characteristics can help you make the best decision.

Here we look at several aspects of both mineral wool and fibreglass insulation, including composition, ease of use, thermal performance, lifespan and durability as well as fire resistance to help you make a decision on which to choose.

Composition

What is mineral wool insulation?

Mineral wool, made from natural stone, is recycled slag (a by-product of steel production), or silica, and is manufactured by melting these materials and spinning them into fibres.

Sometimes called stone wool, it’s dense, durable and offers good thermal, acoustic, and fireproofing properties. You’ll often find it used in more heavy-duty settings, like industrial applications, but it’s just as suitable for residential projects where high performance is needed.

What is fibreglass insulation?

Fibreglass insulation on the other hand, is made mainly from recycled glass, which again is melted and spun into fibres, creating a wool-like material.

This type of insulation, sometimes called glass wool or even glass mineral wool, is the classic insulation quilt most people are familiar with, often sold in rolls or pre-cut batts. Because it’s lightweight and affordable, fibreglass is popular for DIY projects like insulating lofts or insulating a wall.

Application

Mineral wool is versatile and can be used in various settings, including floors and. walls, for insulating roofs, and even around pipes. Its density makes it particularly good for situations where fire safety and soundproofing are essential.

Fibreglass is used widely in homes and is commonly used to insulate attics, ceilings and for internal wall insulation. It offers good thermal and acoustic insulation, but some argue that it’s not quite as robust as mineral wool.

Ease of use

If you’re handling the installation yourself, fibreglass is probably the more straightforward option. It’s lighter and more flexible, so it’s easier to cut and fit, especially into irregular spaces and around services etc. However, the tiny glass fibres of fibreglass insulation can irritate your skin, eyes, and lungs. So, make sure to wear proper protective gear.

Mineral wool, due to its higher density, is heavier and stiffer, which can make it harder to work with. But, because it holds its shape so well, it’s better for vertical installations like wall cavities, where it won’t sag over time.

Thermal performance

When it comes to keeping your home warm, both mineral wool and fibreglass perform well. However, mineral wool is slightly more efficient at maintaining warmth due to its thermal resistance and density, which means it might take less material to achieve the same level of insulation.

That said, both materials have improved in recent years, and with the right thickness and density, fibreglass can offer similar thermal performance to mineral wool. In quilt form, both offer a thermal conductivity performance of around 0.044 W/mk, which can be as low as 0.032 W/mk when made into dense batts.

Soundproofing

If sound insulation is your priority, mineral wool is the better option. Its dense structure makes it more effective at absorbing sound and reducing noise transmission. This makes it a popular choice in buildings where acoustic performance is important, such as between floors or in walls separating rooms. Fibreglass also provides decent soundproofing, but it’s not quite as effective as mineral wool.

The Building Regs requires a 45-decibel reduction in airborne sound transmission between habitable rooms in domestic dwellings, and both insulation types can meet the 10kg/m3 density required to achieve this.

Fire Resistance

Fire safety is a key consideration in any building, and both mineral wool and fibreglass are non-combustible. Mineral wool, however, has a higher fire resistance – it can withstand temperatures up to 1,000°C. Fibreglass, while still fire-resistant, starts to melt at around 600°C, so doesn’t offer quite the same level of fire protection as mineral wool.

Whilst this all sounds impressive, both insulation products must function as part of a complete system to offer a fire resistance. If you need a specific fire performance, you’re therefore more likely to be choosing a fire tested system rather than an individual insulation product.

Lifespan and durability

Both mineral wool and fibreglass have long lifespans, typically lasting around 50 years or more, if installed and maintained properly. However, mineral wool’s resistance to moisture gives it an edge in durability. It’s less likely to lose its shape or performance over time, especially in areas prone to dampness.

Fibreglass, particularly in its quilt form, is more prone to sagging and moisture absorption, which can reduce its effectiveness over time. If you’re installing insulation in an area where moisture is a concern, mineral wool might be the better choice for long-term performance.

Price

For budget conscious self-builders, cost is always a factor, and fibreglass is generally the more affordable option. Depending on the brand and type, fibreglass insulation can be up to 40% cheaper than mineral wool. Mineral wool’s higher price is justified by its superior fireproofing, soundproofing and moisture resistance, but if these factors aren’t so essential, fibreglass is often the more cost-effective option.

How to choose between the two types

Ultimately, the best insulation material for your project depends on your specific needs and budget.

For cost-effective, DIY-friendly insulation: Fibreglass tends to be cheaper than mineral wool and effectively does much the same job. It’s affordable, easy to handle, and provides good thermal insulation, making it ideal for projects like loft insulation, or acoustic insulation in ceilings or wall.

For superior fireproofing, soundproofing, and durability: Mineral wool is worth the extra cost if you need improved performance. It’s especially suitable for applications where fire safety is a concern, or where noise reduction is critical, such as family homes with teenage kids!

If you are looking for either natural insulation or eco insulation types, consider looking at wood fibre insulation, hemp insulation or sheep wool insulation.

However, it is worth bearing in mind the thickness requirements for thermal performance to satisfy building regulations when making a choice. You can read more in our article on how thick should loft insulation be.

The Notting Hill home of Iya Patarkatsishvili, daughter of a Georgian billionaire, has become ground zero for a high-profile legal dispute.

Purchased for £32.5 million, the Victorian mansion is now allegedly overrun with moths due to wool insulation embedded in its walls and ceilings.

Patarkatsishvili and her husband, Dr Yevhen Hunyak, are suing the previous owner for £36 million, claiming damages to carpets, clothing, and furniture, as well as the need to strip and replace the insulation entirely.

Billionaire bug legal battle

The couple accuses seller William Woodward-Fisher, a former GB rowing champion turned property developer, of “fraudulent misrepresentation” for failing to disclose prior moth problems. The pre-sale questionnaire, they claim, omitted mention of infestations under the “vermin” category.

“Our home has been turned into a nightmare,” the couple stated in their legal filings, alleging moth-related damage to carpets, furniture, and even food supplies. Their children’s toothbrushes, they claim, were not spared.

They are seeking £9.6 million to remove and replace the sheep wool insulation, along with reimbursement for the purchase price and associated taxes.

Woodward-Fisher disputes the claims, asserting that he had no obligation to disclose the presence of moths in the house, and that repair costs would total a far more modest £162,652. His legal team argues that moths do not fall under the definition of vermin. “We tend to view that as four-legged furry things with long tails,” said one solicitor.

Moth surge linked to changing habits and rising temperatures

The Patarkatsishvili lawsuit highlights a broader issue: a surge in moth infestations. Organisations like English Heritage have reported a 216% increase in moths over recent years, and pest control companies have seen a sharp rise in calls.

Experts point to two culprits: rising global temperatures and the growing use of biodegradable materials and eco-friendly insulation in homes.

Peter Ward of Heritage House, a property surveying specialist, explains that wool insulation has become a "hot topic" due to its susceptibility to insect infestations. “Suppliers didn’t fully consider the risks when they began using untreated wool. The result is cases like this,” Ward notes.

That said, many branded eco insulation manufacturers now treat wool with chemicals like borax to deter bugs, although it is not clear if this was used in the Patarkatsishvili house.

Who bears responsibility for moth infestations?

As eco-insulation becomes more popular, legal and ethical questions arise around disclosure, accountability and even certification as to whether eco insulation types have been treated to prevent pests.

In the case of the Notting Hill mansion, Patarkatsishvili accuses the seller of fraudulent misrepresentation for failing to disclose a previous moth problem. Woodward-Fisher’s defense hinges on the definition of “vermin,” which doesn’t typically include moths.

Surveyors face limitations, too. They can flag visible signs of infestation but aren’t authorised to perform invasive inspections unless specifically instructed. Future consumer guides from institutions like RICS aim to clarify this.

Property consultant Tom Tangney advises cautious buyers to look for signs of moth damage and request warranties from sellers that insulation has been treated.

While well-installed insulation can lead to significant savings on your heating bills, there are some areas where adding insulation can do more harm than good – to both your wallet and the fabric of your home.

In certain spaces, the risks of placing insulation incorrectly can outweigh the potential benefits. For example, insulating areas prone to moisture can lead to dampness and mould growth, which can damage your property and impact your health.

From unventilated loft spaces to moisture-prone basements, this guide will cover the specific areas in the home where insulation should be avoided or approached with caution.

1. Moisture-prone basements or crawl spaces

Insulating moisture-prone areas, such as basements or crawl spaces, may seem like a good way to improve your home's energy efficiency, but it often leads to bigger issues down the line.

When moisture isn't managed properly, it can become trapped within a structure, leading to mould growth, which poses health risks and can also compromise your home's structural integrity.

Similarly, cellars and unventilated utility rooms are often prone to damp, due to their below-ground location and limited airflow. To avoid these problems, conduct a thorough moisture assessment and address any existing damp issues first.

"If you’re insulating those areas, you really need to think about the system design. That might mean improving drainage, using vapour-resistant materials, or insulating in a way that allows the structure to breathe. Just adding insulation to a damp space rarely ends well," says Michael Zahouri, founder of Pyramid Eco.

2. Solid walls with no damp-proof course

"The relationship between insulation and damp is a complicated one," explains Joanna O’Loan, knowledge manager at the Energy Saving Trust. "There are occasional accounts of insulation being blamed for causing damp issues. However, this typically results from improper installation or choosing an unsuitable type of insulation for the home.

"That being said, it's important to understand that insulation alone won’t solve an existing damp problem either. In fact, it can sometimes worsen the issue or shift it to another area."

For example, Joanna highlights that a leaky roof might channel water down an open cavity. If you then install cavity wall insulation without addressing the leak, that water needs to find a new path, potentially exposing or aggravating a pre-existing issue.

Older homes with solid walls that lack a damp-proof course therefore pose a unique challenge. Adding insulation to these walls without first addressing any existing issues can lead to something known as interstitial condensation – moisture trapped within the wall, causing internal dampness and potential long-term structural damage.

To avoid these issues, before insulating a wall, you should asses and treat your walls for underlying moisture issues. Otherwise, you may insulate your internal walls only to find persistent damp patches and peeling plaster emerging soon after.

3. Electrical boxes, wiring and lighting

"Electrical components need space to release heat. The danger is that the heat builds up instead of dissipating," says Michael Zahouri. "Take recessed lights as an example – older fittings can get very hot. If insulation is covering them, it increases the risk of overheating and in some cases can become a fire hazard. That’s why many lighting fixtures have clearances specified around them."

Covering junction boxes can make future electrical work difficult and may violate building codes that require easy access for inspection and repairs. Insulating these components can also prevent them from functioning as intended.

To avoid these problems, make sure you leave a safe gap between insulation and any electrical elements or use protective barriers that allow for proper airflow. This simple step helps prevent safety issues while still keeping your home energy-efficient.

4. Areas near water pipes without consideration for access

In the same vein as electrical components, insulating too close to water pipes or plumbing systems can create complications down the line. If pipes are insulated without leaving room for access, maintenance can become a challenge, and any potential leaks may go unnoticed.

Hidden leaks can lead to undetected water damage, mould growth, and even structural issues, so avoid these problems by keeping water pipes accessible and applying insulation to these areas thoughtfully, leaving space for inspections and repairs when needed.

"Pipes also expand and contract slightly as water temperature changes. Leaving some space around them helps avoid pressure on the pipework and makes it easier to inspect or repair when needed," Michael Zahouri adds.

5. Loft spaces without ventilation

Without sufficient airflow, moisture from the living spaces below can rise and condense on cooler loft surfaces, soaking into wooden elements and causing structural damage and decay.

Therefore, the Energy Saving Trust advises that insulation should not be installed where it is likely to block existing ventilation points, such as eaves or soffit vents, as this can lead to loft condensation and damp issues. In addition to these measures, loft hatches should be draught-proofed to stop warm, moist air from entering and exacerbating these problems.

Inadequate insulation coverage or gaps around structural beams in your loft can also cause thermal bridging, where heat escapes through poorly insulated areas. This can lead to temperature fluctuations and moisture build-up, further reducing the effectiveness of your insulation.

To avoid thermal bridging, ensure that insulation is continuous and overlaps properly, covering potential gaps around beams and edges. Using high-quality insulation materials and working with a professional to assess hard-to-reach areas can also help maintain consistent coverage.

6. Around chimneys and flues

Always exercise caution when insulating areas near to chimneys and flues, as insulation too close to these heat-generating structures can pose a serious fire risk and may also hinder airflow.

The DLUHC’s Approved Document B: Fire Safety suggests a minimum distance of at least 50mm between insulation and flue pipes or chimneys. This gap allows heat to disperse and prevents direct contact that could put your home at risk.

For added safety, you can also use fire-resistant materials, like mineral wool insulation, in areas near to chimneys or flues. When in doubt, always check current building regulations or consult a professional to make sure your insulation project is up to code.

7. Directly behind timber cladding

If there is no drained and ventilated cavity, insulating behind timber cladding is very risky, according to Mike Bekin, Managing Director of Ecochoice.

He explains, "Many cladding systems depend on a ventilated rainscreen gap so wind-driven rain and absorbed moisture can dry out. Packing insulation tight behind cladding, or omitting the cavity and breather membrane detailing, can trap moisture against the back of boards and battens, leading to distortion, staining and decay."

FAQs

Should you insulate bathrooms?

Yes, it's generally a good idea to insulate bathrooms, as it can help maintain consistent temperatures and improve your home's energy efficiency.

However, you need to exercise more caution in these spaces due to the higher moisture and humidity levels. Opt for moisture-resistant insulation in these spaces and always ensure you have adequate bathroom ventilation to prevent potential issues like condensation or mould.

Is it a bad idea to insulate your home yourself?

Your ability to insulate your home depends on your level of knowledge and DIY experience. In general, most homeowners can safely add loft insulation themselves.

However, more complex projects like cavity wall or spray foam insulation typically require professional installation to ensure both safety and effectiveness..

"In general, insulation works best when it is installed with the building systems in mind. You want to improve energy efficiency without creating hidden moisture pockets or blocking access to important components," concludes Michael Zahouri.

There's no doubt that learning how to insulate your house is a smart way to boost energy efficiency and comfort. These eight types of eco insulation are a good place to start your research if you want to explore your green options.

The question of how to insulate a Victorian house is a common one asked by homeowners living in this type of property. While these houses feature beautiful architectural details and are usually full of character, they are not without their issues – and one of the most common is that they can be rather chilly to live in.

Perhaps you are looking at how to insulate your house having just moved into a renovation project, or maybe you have been living for some time in your home and have had enough of rising energy bills and uncomfortable draughts. Whatever it is, there are plenty of ways of adding in insulation in order to solve both issues.

"Victorian houses were originally built with little to no insulation," explains Samuel Hitch, MD at Buy Insulation Online Ltd. "This was because they focused on allowing the property to breathe, that is, allow pent up moisture emitted from the often large households crammed inside to escape. Ventilation was considered more important than heat retention, and coal etc was relatively cheap so it was preferable to build a house that could breath, was structurally stable and protected from damp than preventing heat loss and so on."

In the case of Victorian properties, that is, those built between 1827 and 1901, adding in insulation can be a little more complicated than with some newer buildings, but don't worry, our guide is here to help.

How to insulate a Victorian house with solid walls

One of the first obstacles when it comes to insulating a Victorian property is that, unlike more modern houses, they tend to have been built with solid walls as opposed to cavity.

"Victorian houses are built with solid walls, meaning there is no internal cavity with insulation like there is with modern houses," explains architect Graham Ford of Graham Ford Architects.

"You can go for internal insulation during a room renovation or even external insulation if you’re up for a more significant investment," picks up Blerta Morina, sales executive at Trade Warehouse.

"In some cases you can add the insulation to the outside walls and then add a render," continues Graham Ford. "However this is the exception rather than the rule."

"External wall insulation provides excellent thermal performance and protects existing brickwork," explains Samuel Hitch. "However, it requires scaffolding, may alter the building's appearance and the installation process can be messy."

For this reason, internal insulation is usually the preferred option but it is still not without its challenges.

"In most cases you will need to add at least 75mm to 100mm to the internal walls," explains Graham Ford. "The big issue with this is the loss of internal floor area. You need to get advice from your architect on the impact of wall insulation on your internal space and your options for reducing its thickness.

"You can instead compensate by increasing insulation in roofs and floors if possible. Wall insulation is better if it is hydrophobic so moisture can pass through so there are no issues with the insulation being placed against the brick."

Adding floor insulation to a Victorian house

As solid walls are a little tricky to insulate in Victorian houses, a brilliant way to increase their thermal efficiency and help them to feel warm and cosy is to turn your attention to insulating floors.

"Many floors of Victorian houses are built with timber joists," says Graham Ford. "One option is to lift the floorboards and add insulation between the joists. You can fit mesh or breather membranes stapled to the sides of the joists to support the insulation and we would recommend the insulation is moisture resistant.

"It is essential the void area under the joists is well ventilated," continues Graham. "You will be able to see the vents in the external brick walls at low level next to the pavement. If you are insulating between joists you will need to place a polythene sheet on sand blinding and gravel to restrict the passage of moisture. This could be difficult with an existing floor so speak to your architect about options."

"Placing mineral wool or breathable insulation between the joists helps prevent draughts from below," adds Samuel Hitch. "Rugs and carpets with insulating underlays can also help retain warmth."

While insulating suspended floors is usually pretty straightforward, in some cases you will find you are dealing with a solid concrete floor, in which case things are a little more complicated.

"If you have a concrete floor then your options are much more limited as adding insulation would increase the height of the floor and this would normally impact everything from skirting to doors," explains Graham.

"Many Victorian homes have been retrofitted with solid concrete floors, often in kitchens or extensions," further explains Samuel Hitch.

The usual way to insulate a solid floor is to lay a damp-proof membrane over the concrete before a layer of rigid foam insulation before finally having the whole thing screeded. Older homes were designed to be breathable and concrete is not – meaning you could run into issue with damp.

"Using Karndean or some other insulated lino finish (instead of tiles or wood) may help a little with insulation too," adds Samuel.

One option is to dig up the entire floor and start again, but this is best left for major renovation projects.

Insulating a Victorian roof

The roof of a Victorian house is another heat loss hotspot so it pays to take a look up there to see what can be done to minimise this.

"Most Victorian houses have tiled roofs on a timber structure," begins Graham Ford. "This means there is space between the rafters to place insulation.

"The big issue with insulating roofs is condensation. Normally in these old houses the underlay is not breathable so if you add in insulation and there is not enough ventilation, you will suffer from condensation in the loft," continues Graham. "We recommend checking first to make sure if the underlay is breathable or not. If it is not then we recommend replacing it with a breathable underlay and ensuring there is a ventilation gap above the roof insulation.

"You will need vents at the top of the roof and at the eaves for air flow. You should be aware that replacing an existing non-breathable underlay involves removing the roof tiles so check with your builder and architect before proceeding as this will be a big cost."

"This is the easiest and most cost-effective area to insulate," picks up Samuel Hitch. "Aim for 270mm depth of insulation material, do not block soffit vents and ensure adequate ventilation in the loft space."

Insulating windows and doors

In many old houses, windows and doors can be ill fitting and therefore draughty, not to mention the fact that some still feature single glazing or may have failing frames. For this reason, properly draught proofing windows and doors will make the world of difference to how comfortable your home feels to spend time in as well as to your energy bills.

"Doors and windows are often the culprits behind those constant chills," explains Blerta Morina. "Sealing gaps around frames and doorways is an easy and budget-friendly fix, with window secondary glazing as another good option if full replacements are too pricey."

Use caulk or sealant to fill in any gaps around door and window frames and ensure any rotten sections of timber are repaired.

Adding in weatherproofing is another cheap and easy way to block out cold draughts – as is simply using draught excluders and thick curtains with a good thermal lining.

Three brilliant draught proofing buys