What is insulation board — and is it the best option for insulating my project?

Insulation board will enhance the energy efficiency of a property
Insulation board will enhance the energy efficiency of a property (Image credit: Getty Images)

Choosing insulation is a key part of a self build or renovation project but with many types to choose from - with different pros and cons - it can be a daunting task. 

Insulation board is often top of the list for many undertaking building work, as it can be easy and quick to install to help stabilise temperatures indoors and potentially help reduce energy bills. Insulation boards generally take the form of big panels and can be incorporated into floors, ceilings, and walls, but there are still a variety of different materials and thicknesses to select from.

Not to mention building regulation requirements dictating your minimum home insulation U-value. Here we answer the question: 'What is insulation board' as well as taking a deep dive into all the different types of board to help you make your choice.

What is insulation board?

Insulation board is generally a rigid, flat board of insulating material. This can be anything from foamboard, wood fibre board or board made of polystyrene. Insulation board can be used in the roof, floor or internal cavity walls to trap heat in the home as well as providing an element of soundproof the property. They tend to be low thermal conductors, meaning they're good at keeping heat in the home. This results in cool summers and warm winters.

Stephen McNeil, a construction specialist and founder of Pro Roof Scotland, says: "Insulation is crucial to any renovation, extension, or self-building project. It's built into the fabric of the structure and will keep people warm in the winter without paying extortionate amounts on their heating bill. It also prevents damage from rot and mould.

“Lining insulation installation up so it coincides with building work is a sensible choice as there likely won't be a better time to get it done.”

What different types of insulation board are there?

1. PIR (polyisocyanurate) board is a sturdy combination of isocyanates and polyols. It is so effective you only need half the thickness compared to other insulators. PIR leads to less waste, which makes it one of the most environmentally friendly insulators available.

2. EPS (expanded polystyrene) board is a stiff thermoplastic material. It weighs less, yet is bulkier, than regular polystyrene. Like regular polystyrene, it is hazardous for the environment and is notorious for being one of the leading causes of plastic pollution.

3. Extruded polystyrene (XPS) is a high-performance form of rigid insulation with a closed cell structure which makes it impervious to moisture. It is available in various grades for specific applications, such as resistance to excessive moisture levels.

4. Wood fibre boards are an eco-friendly option made from recycled wood pieces which would have otherwise been wasted. Rigid and heavy-weight options are great at providing sound insulation benefits.

5. Sheep wool insulation is great for those looking for an environmentally-friendly option. It can run on the more expensive side, but it is extremely effective at reducing heat loss. However, Homebuilding and Renovating’s Tim Pullen says the wool will need to be twice as thick as other types of insulation.

Insulation board and U-values

When considering insulation, it is important to understand U values, also known as thermal transmittance, which measures the rate of transfer of heat through doors and windows in the home. Usually, they are represented on a scale of 0-1, and the lower the number, the more effective the insulation is performing.

Dave Raywood, marketing and procurement director at HSS Pro Service, says: “It’s always important to check with your local planning authorities to ensure you have the most up-to-date information. The maximum U-value for Windows is 1.4W/m²K, which I believe is a 0.2 decrease from the previous year, encouraging homeowners to seek more energy-efficient choices.”

This will impact the size and type of insulation board you need for your project. It is also worth bearing in mind that several types of insulation board can have a higher U-value than some other insulation types, making this a good choice if you don't have the luxury of space for more insulation material in your build.

Insulation board and building control

Insulation board will also help renovators meet Building Regulations Part L, which covers the conservation of fuel and power in the building of new homes in England, and establishes how energy-efficient new and existing homes should be.

In June 2022 there was an important update to the Building Regulations which includes an uplift to Part L, where all new homes must produce 31% less carbon emissions.

The changes could affect anyone undertaking a home improvement project, extension, renovation or self-build as it dictates minimum U-values and therefore the size and type of insulation you need.

Where can insulation board be used?

Insulation boards are an ideal choice to use in roofs, floors, and cavity walls as these are the parts of the home that take the brunt of the bad weather. However, insulation board can be used anywhere as long as there is enough space for it.

It is worth noting that Insulation board for underfloor heating can be a more specialist type of board and may be different depending on where you plan to install it – ground floor or first floor – as well as how much height in a room you have to play with. 

Sam Webb

Sam is based in Coventry and has been a news reporter for nearly 20 years. His work has featured in the Mirror, The Sun, MailOnline, the Independent, and news outlets throughout the world.  As a copywriter, he has written for clients as diverse as Saint-Gobain, Michelin, Halfords Autocentre, Great British Heating, and Irwin Industrial Tools. During the pandemic, he converted a van into a mini-camper and is currently planning to convert his shed into an office and Star Wars shrine.