Draughts account for up to 20% of heat loss in an average UK home. That’s hundreds of pounds per year escaping through gaps around windows and doors that you can feel with the back of your hand on a windy day. Draught-proofing is one of the cheapest energy-saving improvements you can make — most materials cost under £5 per door or window, and the job takes minutes rather than hours.
Finding the Draughts
On a windy day, slowly run the back of your hand (or a lit incense stick) around the edges of your windows and doors. Where you feel cold air coming in (or see the smoke deflect), that’s a draught that needs sealing. Common draught points include:
- Around the edges of opening windows (where the window meets the frame)
- Around door edges (top, sides, and bottom)
- Through letterboxes
- Under doors (the bottom gap)
- Around loft hatches
- Through keyholes on older doors
- Where pipework enters through walls
Types of Draught Excluder
| Type | Best For | Lifespan | Cost | Difficulty |
|---|---|---|---|---|
| Self-adhesive foam strip | Window edges, door edges | 1–3 years | £2–£5 per roll | Very easy |
| Rubber/EPDM seal | Window edges, door edges | 5–10 years | £5–£10 per roll | Easy |
| V-strip (metal or plastic) | Sash windows, door edges | 10+ years | £5–£15 | Easy-moderate |
| Brush strip | Door bottoms, sliding sashes | 5–10 years | £5–£10 | Easy |
| Door bottom seal (drop-down) | Door bottoms | 10+ years | £10–£25 | Moderate |
| Letterbox draught excluder | Letterboxes | 5–10 years | £5–£10 | Easy |
| Keyhole cover | Old-style keyholes | Permanent | £3–£8 | Very easy |
Draught-Proofing Windows
Casement Windows (Side-Hinged)
- Clean the frame where the window closes against it — remove any dust, old paint, or debris
- Measure the length of each edge that needs sealing
- For a budget fix, apply self-adhesive foam strip along the frame where the window closes. Press firmly for a good bond. Choose a thickness that fills the gap without preventing the window from closing
- For a longer-lasting fix, use self-adhesive EPDM rubber seal — it compresses better than foam and lasts much longer
Sash Windows
Sash windows are notoriously draughty because they have moving parts that create gaps on all four sides. For proper sash window draught-proofing:
- Between the sashes: Fit a brush strip or V-strip where the two sashes overlap (the meeting rail)
- Sides of the sashes: Fit brush strips into the staff beads (the strips that hold the sashes in place). This requires removing the beads, routing a groove, inserting the brush strip, and refitting the beads — a moderate DIY job
- Top and bottom: Fit brush strips or EPDM seals to the top rail and bottom rail
Professional sash window draught-proofing costs £200–£400 per window but is very effective. The Energy Saving Trust draught-proofing guide estimates that proper draught-proofing saves £60–£100 per year on heating bills for an average home.
Draught-Proofing Doors
Door Edges (Sides and Top)
Apply self-adhesive foam or EPDM rubber strip to the door frame (not the door itself) where the door closes against it. Close the door and check that it still shuts properly — too thick a strip and the door won’t latch.
Door Bottom
The gap under a door is often the biggest single source of draughts. Options include:
- Brush strip — screws to the bottom of the door. Cheap, easy, and works on uneven floors. Doesn’t drag on carpet
- Automatic drop-down seal — a spring-loaded seal that drops when the door closes and lifts when it opens. More expensive but very effective and doesn’t drag on the floor. Mortises into the bottom edge of the door
- Threshold strip — a metal or rubber strip that screws to the floor/threshold. The door closes against it. Works well for external doors
Letterboxes
Fit a letterbox draught excluder — either a brush-strip type that screws over the inside of the letterbox, or a hinged flap type. Both are cheap (£5–£10), easy to fit, and make a noticeable difference. The bristle type is less likely to interfere with post delivery.
What NOT to Draught-Proof
It’s important not to seal everything. Some ventilation is essential for health and safety:
- Never block trickle vents in windows — these provide background ventilation that prevents condensation and mould
- Never seal bathroom or kitchen extractor fan vents
- Never block air bricks — these ventilate the underfloor space in older houses. Blocking them leads to damp and timber decay
- Rooms with gas appliances need adequate ventilation. Check with a Gas Safe engineer before sealing a room with a gas fire or boiler. Our condensation guide explains the balance between ventilation and warmth
Cost vs Savings
| Job | Material Cost | DIY Time | Annual Saving (est.) |
|---|---|---|---|
| All windows (foam strip) | £10–£20 | 1–2 hours | £25–£50 |
| All external doors (complete) | £20–£40 | 1–2 hours | £20–£40 |
| Letterbox excluders (all doors) | £10–£20 | 30 minutes | £5–£15 |
| Loft hatch seal | £5–£10 | 30 minutes | £10–£20 |
Total investment: under £100 for an entire house. Typical payback period: under one year. After that, it’s pure savings — every year. As the Which? draught-proofing review notes, this is the single best return on investment of any home energy improvement.
