How do I reduce draughts?

Draught-proofing is the cheapest meaningful thing you can do to a cold house, and the payback is usually measured in months. The one rule that matters: seal the accidental gaps, never the deliberate ones. A house with no ventilation gets condensation, mould and, where there are fuel-burning appliances, a genuine safety risk.

Safety

What you'll need

• Self-adhesive draught excluder strip
• Letterbox brush cover and keyhole escutcheon
• Silicone sealant or decorator's caulk
• Door brush strip or draught excluder
• Floorboard gap filler (optional)
• Chimney balloon for an unused fireplace (optional)

Step by step

1. Find the draughts on a cold, windy day — a lit incense stick or a damp hand shows the airflow.The smoke visibly bends where air is moving. It finds gaps you'd never guess.
2. Fit self-adhesive foam or brush strip around opening windows and doors.Clean the surface with alcohol first — the adhesive fails on dusty or greasy frames.
3. Fit a brush strip at the bottom of external doors and a cover on the letterbox and keyhole.The gap under a front door is often the single largest hole in a house.
4. Caulk the gap between skirting and floor, and between skirting and wall.Decorator's caulk stays flexible. It's a surprisingly large combined area in an older house.
5. Fit draught strip around the loft hatch and make sure it closes onto it.Warm air rises, so the loft hatch leaks more heat than its size suggests.
6. Block an unused chimney with a chimney balloon or a purpose-made cap — but leave a vent.A completely sealed flue traps moisture and causes damp. Purpose-made products include a small vent for this reason.
7. Leave every air brick, trickle vent and extractor alone.These are the house's designed ventilation. Sealing them creates condensation and, near any appliance, a safety hazard.

Tips

• Do the cheap wins first — letterbox, door bottom, loft hatch. They typically account for a large share of the total draught for a very small spend.
• Heavy lined curtains that reach the floor make a measurable difference to how cold a room feels, and cost nothing to close.
• Draught-proofing a sash window is fiddly but very effective; brush-pile strips designed for sashes are the right product.
• Don't seal a room so well that a gas appliance is starved of air. If a room has any fuel-burning appliance, ventilation requirements apply.

Common mistakes

• Blocking air bricks — They provide combustion air and underfloor ventilation. Blocking them risks carbon monoxide and rot.
• Sealing trickle vents — They're the designed background ventilation. Closing them is a leading cause of new condensation problems.
• Fully sealing an unused chimney — Trapped moisture causes damp in the stack. Use a vented product.

Questions people ask