How to insulate windows – try these 10 easy ways to keep your house warm

Soaring energy prices and what seems like a never ending run of 'cold snaps', means insulating windows is even more important than ever right now.

Insulation and airtightness are key in helping to keep our homes warm during the winter, and cooler in summer. However, while some measures are relatively cost-effective and cheap to undertake (such as insulating a loft), others such as external or internal wall insulation can cost thousands.

If you are wondering how to insulate windows, then our round up of the best methods out there is here to save the day. We've got solutions for every situation and all budgets.

1. Insulate windows with weather stripping

Weather seals or weather stripping is a brilliant, quick and inexpensive way of insulating windows. Costing from as little as £5 per roll, one of the most common types of draught seal is the self-adhesive foam strips that can be purchased in coils ready to be cut to length.

Alternatives products for draught proofing windows include brush seals, spring metal and v-strips – all of which will, as the name suggests, seal up any gaps around windows to prevent cold draughts.

Sam Wheat, expert at The Sustainable Haus, says, "It's not insulation, but it cuts draughts, which can help control the climate in a building. You can do it yourself, but it's only effective if draughts are a problem, such as in older or poorly fitting windows."

Sam Wheat

Sam Wheat is a sustainability-focused retrofit consultant specialising in practical, high-impact upgrades for UK homes. Through The Sustainable Haus, he helps homeowners move toward EnerPHit and Passivhaus standards – whether as an ambition or a clear design goal. Sam’s approach is grounded in real-world fixes: improving airtightness, upgrading glazing, tackling drafts, and guiding clients through smart, staged interventions that genuinely transform comfort and energy performance.

2. Apply caulk to your windows

Caulk is a DIYer's best friend and is a particularly effective way of insulating windows too. Use it to seal gaps between the window frame and wall, as well as all the joins in and around the frame.

Before you begin, scrape away any peeling old paint or caulk, then use a caulking gun to neatly apply new silicone caulk.

Sam Wheat says, "Over time caulk can become brittle and start to leak, so removing it and recaulking can improve the airtightness of the building."

3. Try window film

Installing window film is a really popular way to insulate windows – cheap to buy, easy to fit and effective. Window insulation film is made from plastic and is often sold in kits that include everything you need to apply it, including tape.

To apply window film you must first ensure your window is sparkling clean, before measuring it and cutting the film to size. Manufacturer's instructions usually state that you should leave a little allowance in size around the edges. The tape is then applied around the frame ready for the film to adhere to it.

Once you are sure there are no creases or wrinkles in the film you need to apply heat to shrink it for a tight fit – this is usually done with a hairdryer. Window film is easy to remove once you no longer need it but be aware that the tape can sometimes take paint with it (particularly from old timber window frames).

Michael Arrowsmith, expert at Etheridge Windows, says, "It works by creating a small pocket of still air between the film and the glass. It is not a replacement for proper double or triple glazing, but on single-glazed windows you can really feel the difference during a cold snap."

Michael Arrowsmith

Michael Arrowsmith is the Sales Manager at Etheridge Windows. He brings several years of hands-on experience and a deep understanding of modern window technology. Whether he’s explaining the benefits of triple glazing or guiding customers toward the most energy-efficient options for their property, he’s known for his simple, helpful advice.

4. Fit secondary glazing

Secondary glazing is a popular way of insulating windows amongst those living in listed buildings and in conservation areas, where new double glazing might not be deemed acceptable. It is also cheaper than installing new double glazing.

Secondary glazing can also add a soundproofing layer, as well as reducing the chance of window condensation – it can even add a level of security.

Fitting secondary glazing usually involves adding a slimline, second window to the inside of an existing window frame.

Secondary glazing comes in many forms, with frames available in uPVC, aluminium and timber. Systems can be temporary, designed to be taken in and out as needed, or permanent. They can slide open, be permanently fixed or open like a regular casement window.

Michael Arrowsmith says, "Secondary glazing is a strong step up in performance. By adding a second pane on the inside, you create a sealed air gap that acts as a thermal barrier. It is particularly valuable in listed buildings or homes where you are not allowed to replace the original windows, and it often improves noise levels too."

5. Replace single glazing

Although replacing single glazing with double glazing is not suitable for every type of property (period properties can lose some of their character, for example), it could make a huge difference to how well your home retains heat in the winter. Double glazing can also prevent overheating in the summer.

Before rushing to replace all your glass with double glazing, however, do address draughty window frames and other sources of heat loss – otherwise your double glazing costs just won't be worth it.

Michael Arrowsmith says, "Replacing single glazing offers the biggest long term improvement. Modern double glazing significantly reduces heat loss and helps keep rooms at a steady and comfortable temperature. It is the most reliable way to boost energy efficiency, cut bills and reduce condensation."

6. Hang thermal curtains or blinds

Thermal curtains and blinds are one of the best ways to insulate windows – and providing you buy good-quality products, they should also prevent rooms from overheating in the summer months.

Thermal curtains are made from at least three layers of material that work together to control the temperature of a room. It is also possible to buy thermal blinds. These usually feature tiny honeycomb pockets or similar that trap the air to create a warm, cosy room.

Michael Arrowsmith says, "Thermal curtains or blinds work by creating a warm buffer between the room and the cold glass. They are especially helpful at night. While they do not stop draughts coming through the frame, they do make the room feel cosier by slowing the heat loss from inside."

7. Use bubble wrap as insulation

Not a solution that everyone will jump at, but an effective one nonetheless – just don't expect to be enjoying any views when you open the curtains.

Those in the know suggest misting the windows with water before taping bubble wrap (bubble side to glass) to the window.

Michael Arrowsmith says, "Bubble wrapping windows might sound like a makeshift fix, but it does a decent job when you need something temporary. It traps air against the glass in the same way window film does. It is often used in garages, sheds or rental situations where a quick boost is needed before committing to new glazing."

8. Consider draught snakes

A draught snake or excluder is a simple and easy way to draught proof your windows. They are simply small, long, tube-like cushions that sit on your window sill to block any gaps around your window frame.

Michael Arrowsmith says, "They will not insulate the window itself, but they help block shallow draughts in older homes. They are ideal for specific problem spots where you can feel the chill at floor level."

9. Apply a low-E coating

Low-emissivity (low-E) glazing works by absorbing energy created by heating systems inside the building and is extremely effective at preventing heat loss and lowering energy bills. However, in retrofit situations, fitting new Low-E glazing requires new windows to be installed, meaning disruption and significant costs.

Michael Arrowsmith says, "Low E coatings are one of the hidden stars of modern glazing. They reflect heat back into the room while still letting natural light in. Most high performing double- and triple-glazed units in the UK now include Low E glass as standard because it is such an effective way to reduce heat loss without changing how the window looks."

10. Use magnetic secondary glazing

Magnetic secondary glazing is a little different to other types. It is easily removable and held in place by magnets. The best thing about this DIY double glazing is that it is very easy to install, low cost when compared to permanent secondary glazing and still works to insulate windows.

To install it, self-adhesive magnetic strips are attached to the window frame. A magnetic secondary glazing panel is then placed into the frame where it sits snugly. On the downside, some of the cheaper products, made from thin plastic, can be a little flimsy, so check the quality before you buy.

Michael Arrowsmith says, "The magnetic system creates a good insulating air gap and allows you to take the panel off in summer. It is a popular choice for period homes and rented properties where the existing windows cannot be replaced."

When it comes to cutting your heating bills, insulating your windows is one of the most important steps you can take – and now you'll have plenty of ideas to choose from, whether it's a budget-friendly draught snake or permanent double glazing.

Once you've tackled the windows, you might want to learn why insulating a garage makes sense or explore the cost of insulating external walls.