How to insulate windows: 5 hacks to keep the heat in

Draughty windows letting cold air in and warm air out? Don’t despair – we share five inexpensive ways to insulate windows without replacing them.

Draughty windows can be a common problem. Gaps around the frames or where the window closes, as well as single glazing, can all beckon cold air in and suck warm air out. Not ideal when we’re thinking about turning our heating on. We don’t want the energy we’re burning seeping out of our windows when we’re desperately trying to save money on our energy bills. 

So, you’ll be pleased to hear there are ways to help insulate windows without having to replace them.  

Here we share how to insulate windows with some easy and affordable methods.  

foam window draught excluderCredit: Shutterstock / New Africa

1. Add draught excluder tape

Tape is easy to use and fit

If, when you close your windows, there’s still a gap between the frame and the window, apply draught excluder tape, also known as weather sealing tape. This is an inexpensive but quick way to fill the gaps with instant results. Most products are self-adhesive and easy to stick down. They come in different colours and widths so you can choose a size to suit the gap you need to fill. 

Draught excluder tape is usually made from foam such as YIMIKI strong adhesive foam tape, £10.99 from Amazon; or plastic such as TOYMIS plastic weather sealing tape, £8.99 from Amazon. This tape is ideal for casement windows, where the window has a side hinge and opens outwards or top hung windows, where a half window is hinged at the top.  

You can also buy strips with brushes attached, such as the Stormguard door and window strips in white, £10.29 from Screwfix. 

If you have sash windows, then you need to be careful what you use. The sash panes have to slide over each other so there must be nothing to block this action. You can buy window filler seals or strips to fill any voids in a sash window frame.

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How to fit draught excluder tape 

Sally Phillips, director at Chimney Sheep – an online shop for insulation products – explains step by step, how to fix tape to your windows:  

  1. Open the window – the tape must be fitted to make a nice tight seal after the window has been closed.  
  2. Make sure the surface you are fitting it to is clean and dry.  
  3. Unroll the tape and stick it to the sides, top and bottom of the frame, peeling off the backing tape as you work your way around. Press it tight into the inside edge of the frame. You may find it easier to cut it into strips as you work your way around the window.   
  4. Cut the tape at a 45° angle in each corner to get a nice neat fit.  
  5. Close the window as this will help to press the insulation tape into place. 

I used draught excluder tape on my own windows 

My home has double glazing but the seal between the window and frame on some of them had disintegrated, leaving gaps. I could hear the wind whistling through and could feel a draught if I was standing next to them. I used self-adhesive foam tape to close up the gaps. A year on and it’s still working well. Cheap and quick to do as a one-person job – it only took a few minutes to fix it in place.   

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2. Hang thermal curtains and blinds

Window dressing material can aid thermal comfort

Hanging curtains and blinds can really up the style stakes in a room as well as providing all-important privacy. And while standard curtains and blinds will offer some protection from draughts, thermal varieties have been specifically made to regulate and control temperature.  

Thermal curtains are made from several layers of fabric that include thermal fabric. They work by capturing cold air before it makes its way into a room, while also preventing warm air from escaping. Thermal blinds work in a similar way. They often consist of a double-layered honeycomb design – the honeycomb-shaped pockets trap air. 

As there may be slight gaps round the edges of the thermal curtains or blinds when they’re hung up, it’s best to pair them with other draught-proofing methods for maximum impact. 

Purple thermal curtains, full lengthCredit: Julian Charles

How much money can draught proofing save you?  

According to the Energy Saving Trust, draught proofing around windows and doors could save you around £50 a year. These savings are based on “a typical gas-fuelled semi-detached property in England, Scotland or Wales. Figures for England, Scotland and Wales are based on fuel prices under the Energy Price Guarantee running from April 2023 to the end of June 2023. 

3. Try window gap filler

Caulk, expanding foam or wool filler are three options

If you’ve got unsightly gaps between any window frames and the sill, then there are fillers you can use to block them up. 

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Caulk 

Caulk can cover up a multitude of sins and can be used to help fill gaps around your windows. Caulk is flexible and many can be painted over once cured. You will need to load the sealant tube into a sealant gun in order to use it, but this will give you precision when you run the sealant into the gap. 

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caulk being used to fill gaps along window edgeCredit: Shutterstock / veryulissa

Expanding foam 

Expanding foam is another option. It works exactly as it says on the tin, by expanding into the gap it’s sprayed into. Many foams can be sanded afterwards for a neater finish.

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Soudal gap filler expanding foam, 750ml, Screwfix

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Wool gap filler

If you’d like a sustainable alternative, then you can use wool gap filler. “It’s much more sustainable than expanding foam, but also much more controllable,” says Phillips. “You can just poke small pieces of it into place to block gaps and cut off draughts.”

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Wool gap filler, Chimney Sheep

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Wool gap filler, Chimney Sheep

4. Opt for window film

Window insulation film can help combat draughts and condensation

If, like me, you get condensation on your windows then specialist window insulation film (rather than decorative window film) can be a way to try to combat it. The film performs a lot like double glazing because you layer the film over the frame of the window rather than sticking it to the glass.  

It’s relatively inexpensive and readily available. Most kits contain transparent film sheets or a roll and sticky tape. There are generally four or five steps to follow for installation. A pair of scissors and a hairdryer is all you need to fix it to the window frame.

How to fit window film

1. Clean and dry your window and frame.

2. Apply the tape round the edge of the window frame.

3. Roll out or place a large sheet of plastic film over the top of the tape. You must pull it taught.

4. Once it’s in place with no gaps or creases, use the warmth from your hairdryer to create a tight seal between the frame and film. This layer helps to reduce draughts and condensation.

5. Fix magnetic secondary glazing

Add a flexible layer to your windows

Magnetic secondary glazing is not to be confused with permanent secondary glazing, which is often used in period homes with single glazing and installed by a professional fitter. 

Magnetic secondary glazing is a flexible option that you can install and take down as and when you like.  

Like window insulation film, the magnetic secondary glazing creates another ‘layer’ over a single pane or badly performing double glazing. You stick magnetic strips round your window frame and then place a plastic or acrylic sheet, which has a magnetic strip all the way round, over the top to form a bond.  

There are many options online, so it’s worth checking out some reviews to make sure you invest in a good quality product. 

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Easyfix magnetglaze, Secondary DIY Glazing

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Michelle Guy

Written by Michelle Guy she/her

Published:

With an editorial career spanning more than 20 years, Michelle Guy has spent time working on educational magazines and websites as well as being a freelance copy editor for companies like BT, until her career pivoted, and she moved into and embraced the world of homes and interiors.  

Working on magazines and websites including Homebuilding & Renovating, Real Homes and Period Living, Michelle honed her skills writing about all things renovation, extension and self-build. From interviewing homeowners to writing buyer’s guides, from sharing advice about kitchen renovations and extensions to design ideas for bathrooms, Michelle has written about a whole range of home improvement projects for discerning home improvers and keen DIYers alike.