Draughts from windows can lose 10-20% of your heating. The good news? Draught-proofing is one of the cheapest and most effective home improvements you can do.
Where Draughts Come From
Opening Windows (Casement/Sash)
The gap between the opening window and the frame. When seals wear or frames warp, cold air gets in.
Between Frame and Wall
Where the window frame meets the wall. Sealant fails over time.
Through the Glass (Not Really a Draught)
Single glazing feels cold because it doesn't insulate - you feel radiant cold. That's different from air movement.
Trickle Vents
Those small vents at the top of modern windows. They're meant to be there for ventilation - only block them if you have alternative ventilation.
Test for Draughts
The candle test: Hold a lit candle near window edges. If the flame flickers, there's air movement.
The hand test: On a cold, windy day, slowly run your hand around the window frame. You'll feel cold spots.
The tissue test: Hold a tissue near suspected gaps. It'll flutter if there's a draught.
Draught-Proofing Methods by Window Type
Casement Windows (Open Outwards)
Self-adhesive foam strips
The simplest method. Stick foam strips around the frame where the window closes against it.
How to apply:
- Clean the frame thoroughly (the strip won't stick to dirt)
- Wait until dry
- Cut strips to length
- Peel backing and press firmly into place
- Check window still closes properly
Cost: £5-£10 per window Lifespan: 1-3 years before replacing Effectiveness: Good for small gaps
Rubber seals (P-profile or E-profile)
Better than foam - lasts longer and seals better.
- Clean frame
- Measure and cut seal
- Press into place with adhesive backing
- Or fit into routed groove (more permanent)
Cost: £3-£5 per metre Lifespan: 5-10 years Effectiveness: Very good
Sash Windows
Sash windows are draughtier because there are more moving parts and gaps.
Brush strips
Bristle strips fit in the gap between the sash and frame. The brushes flex as the window moves but block air.
Where to fit:
- Between meeting rails (where sashes overlap)
- Between sash and frame (sides)
- At top and bottom
Installation: Usually need routing a channel or fitting a carrier strip. This is one where professional fitting often makes sense.
Sash sealing systems
Complete systems (like Ventrolla or similar) involve:
- Brush strips in purpose-cut channels
- Parting bead replacement
- Staff bead sealing
- Sometimes weights and cords too
Cost: £150-£300 per window professionally fitted Effectiveness: Excellent - transforms performance
Secondary Glazing
Adding a second layer of glazing inside the existing window.
Options:
- Magnetic panels - Removable acrylic panels
- DIY film kits - Shrink-film you heat to tighten
- Fixed secondary glazing - Permanent internal window
Effectiveness: Stops draughts AND improves insulation. Best of both worlds.
Cost: £50-£300 per window depending on method
Frame-to-Wall Sealing
If there are gaps where the frame meets the wall:
Exterior gaps:
- Use exterior-grade silicone or frame sealant
- Needs to be flexible and weatherproof
- May need backer rod for large gaps
Interior gaps:
- Decorator's caulk or silicone
- Can be painted over (caulk)
- Gives neat finish
What About Trickle Vents?
Those small vents at the top of modern windows provide background ventilation. They're there for a reason.
Don't block them unless:
- You have mechanical ventilation (like an MVHR system)
- You're confident your home won't suffer moisture problems
If you must reduce them:
- Cover them only in the worst winter months
- Ensure you have other ventilation
- Watch for condensation increase
Quick Fixes for Renters
If you can't make permanent changes:
- Draught-excluding tape - Removable foam strips
- Window film - Double-sided tape holds shrink film
- Thermal curtains - Heavy curtains help (close at dusk)
- Draft snakes - Block draughts under sashes
What Draught-Proofing Won't Fix
Feeling cold from single glazing: That's radiant cold, not draughts. The glass is cold and you feel it. Solution: secondary glazing or replacement windows.
Condensation: Often caused by too little ventilation, not too much. Don't seal up so much that moisture can't escape.
Failed seals in double glazing: If there's misting between panes, the sealed unit has failed. Needs replacing, not sealing.
Cost vs Benefit
| Method | Cost | DIY? | Payback |
|---|---|---|---|
| Foam strips | £5-£15 | Easy | Months |
| Rubber seals | £15-£30 | Medium | 1-2 years |
| Sash window system | £150-£300/window | Professional | 3-5 years |
| Secondary glazing | £50-£300/window | DIY possible | 2-4 years |
| Frame sealing | £5-£20 | Easy | Months |
Energy Trust estimates £60-£160/year savings from draught-proofing an average home.
When to Call a Professional
DIY-able:
- Self-adhesive strips
- Silicone sealing
- Film secondary glazing
Worth getting help:
- Sash window draught-proofing systems
- Fixed secondary glazing
- If you're not sure what you're dealing with
Want windows sorted properly? I draught-proof windows across Exeter - from quick seal jobs to full sash window systems. Call 01392 964094 or get a quote.
Sam Hembury
Sam is the founder of Hembury Contracting, providing professional handyman services across Exeter and Devon. With years of experience in property maintenance, he shares practical tips to help homeowners tackle common tasks.