If you can feel a cold draught by the window, or the radiator just can’t seem to warm the room, the problem is often the seals. Learning how to insulate windows from the cold without replacing them won’t cost you much: with draught excluder strips, silicone and good curtains, it’s an afternoon’s work. Here are cheap DIY fixes, including how to insulate sliding windows from the cold and old wooden ones.
- Why heat escapes
- 7 fixes without building work
- Sliding windows
- Old windows
- Which fix to choose
- Frequently asked questions
Why heat escapes through your windows
Windows are the weak spot of any façade. According to the Guía práctica de la energía (Practical Energy Guide) published by IDAE, Spain’s Institute for Energy Diversification and Saving, between 25 and 30% of a home’s heating needs are due to heat lost through the windows.
To find out where the air is getting in, do the paper test: close the window on a sheet of paper trapped between the sash and the frame. If it slides out without any resistance when you pull it, the seal isn’t working at that point. Repeat on all four sides.
How to insulate windows from the cold: 7 fixes without building work
1. Self-adhesive draught excluder strips in the gaps
This is usually the fix you notice most. Clean the frame with alcohol, let it dry and stick the strip to the fixed part, where the sash rests when it closes. Foam strips work for small, uneven gaps; profiled rubber strips (E, P or D-shaped) last longer. If the window is then very hard to close, the strip is too thick.
2. Silicone in the joint between the frame and the wall
Check the bead that joins the frame to the wall, inside and out. If it’s cracked, remove it with a craft knife, clean the area and apply neutral-cure silicone or, on the inside, acrylic sealant, which can be painted. On the outside, only work where you can reach without leaning out. Never seal the parts that open.
3. Thermal film or bubble wrap
On single-glazed panes, a clear insulating film creates a layer of air between the plastic and the glass. It’s fixed to the frame with double-sided tape and pulled taut with the hot air from a hairdryer. To insulate windows from the cold with bubble wrap, spray some water onto the glass and press the bubble side against it; it stays in place and comes off in spring. It blocks the view and some of the light, so save it for bathrooms, larders or rooms you rarely use.
4. Lower the shutter and insulate the shutter box
At dusk, lower the roller shutter: the air trapped between it and the glass holds back the cold. If there’s a draught coming from the shutter box, open the inspection cover and line the inside with thin insulation boards, making sure they don’t rub against the shutter as it rolls up.
5. Thick, floor-length curtains
Thermal or tightly woven curtains that reach the floor keep the heat in at night, as long as they don’t cover the radiator. During the day, open them on windows that get the sun.
6. Adjust the locking cams on tilt-and-turn windows
Many PVC or aluminium tilt-and-turn windows have eccentric locking cams on the edge of the sash, which you turn with an Allen key so the sash presses harder against the rubber seal. This is known as the winter setting. Check the manufacturer’s instructions first.
7. Ventilate briefly but well
Once the window is sealed, the moisture in your home has fewer ways out. Air the room for five to ten minutes a day to prevent condensation on windows and mould.
How to insulate sliding windows from the cold
Sliding windows tend to lose more heat: their sashes don’t press against a rubber seal, but close against brush strips. To improve them:
- Vacuum and clean the tracks: dirt stops the sashes from closing fully.
- Replace worn brush strips with new ones of the same size.
- Fit a self-adhesive brush draught excluder where the two sashes meet in the middle.
How to insulate old windows from the cold
Wooden windows that are decades old often have gaps because the wood has moved over the years. Use a V-profile draught excluder, which adapts to uneven gaps, and check the putty holding the glass: if it’s dry or crumbling, replace it with fresh glazing putty. If the window is single-glazed, add thermal film.
Which fix to choose for each problem
| Problem | Fix |
|---|---|
| Draught around the edge of the sash | Foam or rubber draught excluder strips |
| Air between the frame and the wall | Neutral-cure silicone or acrylic sealant |
| Very cold single glazing | Thermal film or bubble wrap |
| Air coming through the shutter box | Line the inside of the box |
| Sliding window that doesn’t close properly | Clean the tracks and replace the brush strips |
If you want to go further, here are some ideas to keep your house warm without sending your energy bill soaring and to make your home cosier with Velia Select’s home products.
Frequently asked questions
How can I insulate windows from both cold and noise?
Rubber draught excluder strips and sealing the frame to the wall reduce both draughts and the noise that comes in through the gaps. For noise that travels through the glass, what really works is replacing the glazing with acoustic glass, and that does mean building work.
Does bubble wrap on windows work?
Yes, as a temporary fix on single-glazed panes: the air in the bubbles acts as insulation. The downside is that it blocks the view.
How often should draught excluder strips be replaced?
It depends on the material and how much the window is used. Replace them when they’re flattened, cracked or coming unstuck: foam strips usually wear out sooner than rubber ones.