Draught-Proofing Your Home: The Cheapest Way to Cut Heat Loss
Draught-proofing is the single cheapest energy improvement you can make. DIY draught-proofing costs £30 to £100 for a whole house and saves £60 to £125 per year on heating. Professional installation costs £200 to £400. Payback is under 2 years either way. Draughts account for 10 to 15% of heat loss in a typical older home, and sealing them makes every other upgrade (insulation, heating) work harder. This guide covers where draughts come from, how to fix each one, what it costs, and when to call a professional.
Where draughts come from
Draughts are uncontrolled air leaks through gaps in your home's structure. They are different from ventilation, which is controlled airflow needed for moisture removal and indoor air quality. The goal of draught-proofing is to seal the uncontrolled leaks while keeping intentional ventilation working.
| Source | Share of air leakage | DIY fix cost | Difficulty |
|---|---|---|---|
| Suspended timber floors | 20 to 30% | £10 to £40 | Moderate |
| Windows (sash and casement) | 20 to 25% | £15 to £50 | Easy |
| External doors | 10 to 15% | £10 to £30 | Easy |
| Chimneys and fireplaces | 10 to 15% | £15 to £30 | Easy |
| Letterboxes and keyholes | 5 to 10% | £5 to £15 | Easy |
| Loft hatch | 5 to 8% | £5 to £15 | Easy |
| Pipe and cable penetrations | 5 to 10% | £5 to £15 | Easy |
| Skirting board gaps | 5 to 8% | £5 to £10 | Easy |
Percentages are approximate and vary by property. Older homes with sash windows and timber floors have the highest air leakage rates.
How to draught-proof each area
Windows
Casement windows (hinged): Apply self-adhesive foam or rubber strip around the frame where the window closes against it. Clean the surface first, cut to length, and press firmly into place. Foam strips cost £3 to £8 per roll and last 2 to 5 years. Rubber strips (P-profile or E-profile) cost slightly more but last longer and seal more effectively. See recommended draught excluder strips for the best options.
Sash windows: The sliding channels are the main leak point. Brush pile strip (a strip of dense bristles in a carrier) fitted into a groove in the sash channel seals the gap while allowing the window to slide freely. This is the gold-standard fix for sash windows. DIY kits cost £15 to £30 per window. Professional sash draught-proofing costs £80 to £150 per window and includes all four meeting points plus the pulleys. See recommended sash window draught-proofing kits.
Trickle vents: Do not seal trickle vents. They provide background ventilation that prevents condensation and maintains air quality. If you find your trickle vents are a significant draught source, they may be damaged and need replacing rather than blocking.
External doors
The gap between the door and frame is the primary leak. Fit self-adhesive strip around the door frame (same approach as casement windows). For the bottom of the door, fit a brush strip or rubber blade excluder that seals against the threshold when closed. See recommended door bottom draught excluders. Letterbox draught excluders (a hinged flap or brush cover) cost £5 to £15 and make a noticeable difference, especially on front doors facing prevailing wind. See recommended letterbox draught excluders. Keyhole covers (a small rotating disc) cost under £5.
Floors
Suspended timber floors (common in pre-1930 homes) are one of the biggest draught sources. Air enters through gaps between floorboards, between the skirting and floor, and through ventilation grilles in the external wall beneath the floor.
Floorboard gaps: Fill with flexible filler, papier-mache, or purpose-made floor gap filler strips. Do not use rigid filler as the boards move seasonally and will crack it out. For very wide gaps (over 5mm), consider having the floor sanded and gaps filled by a floor specialist.
Skirting board gaps: Run a bead of decorator's caulk (not silicone) along the junction between the skirting board and the floor, and between the skirting and the wall. This is one of the quickest, cheapest fixes with immediate impact.
Underfloor ventilation: Do not block air bricks or ventilation grilles in external walls below suspended timber floors. These prevent moisture buildup and rot in the floor timbers. The draught-proofing approach for floors is to seal gaps in the floor surface itself, not to block the underfloor ventilation.
Chimneys and fireplaces
An open chimney loses as much heat as leaving a window open. If you do not use the fireplace, fit a chimney balloon (an inflatable blocker that sits inside the flue) or a chimney cap. See recommended chimney balloons. These cost £15 to £30 and take 5 minutes to fit. Remember to remove the balloon before lighting a fire.
If you have sealed off a fireplace but the chimney is still open at the top, consider having the chimney capped. A cowl or cap prevents rain entry and reduces downdraught. A ventilation grille in the fireplace or chimney breast prevents condensation in the unused flue.
Loft hatch
An uninsulated, unsealed loft hatch is a major heat leak. Fit a strip of self-adhesive foam or rubber around the hatch frame to seal the gap when closed. Add a slab of rigid insulation (50 to 75mm PIR board) to the top of the hatch door with adhesive. This is also covered in our DIY loft insulation guide.
Pipe and cable penetrations
Anywhere a pipe or cable passes through an external wall or ceiling creates a gap. Fill around these penetrations with expanding foam (for large gaps) or decorator's caulk (for small gaps). Common locations include around boiler flue pipes, where water pipes enter from outside, cable entry points, and extractor fan ducts.
Do not seal ventilation for gas appliances
Any room containing a gas boiler, gas fire, or gas cooker needs a permanent air supply for safe combustion. Do not seal air bricks, permanent vents, or trickle vents in these rooms. If in doubt, ask a Gas Safe registered engineer before draught-proofing rooms with gas appliances.
DIY vs professional draught-proofing
| Approach | Cost (whole house) | Time | Best for |
|---|---|---|---|
| DIY (strips, caulk, balloons) | £30 to £100 | 2 to 4 hours | Doors, windows, letterboxes, loft hatch, chimneys |
| Professional | £200 to £400 | Half day | Sash windows, floors, full-house treatment |
| Professional sash windows only | £80 to £150 per window | 1 to 2 hours per window | Period homes with multiple sash windows |
DIY covers 70 to 80% of the benefit for 20% of the cost. Professional draught-proofing is most valuable for sash windows and suspended timber floors.
Savings and payback
| Property type | Annual saving | DIY payback |
|---|---|---|
| Detached house | £125 | Under 1 year |
| Semi-detached | £90 | Under 1 year |
| Terrace | £60 | Under 1 year |
| Flat | £45 | Under 1 year |
Source: Energy Saving Trust. Gas heating at Ofgem Q1 2026 rates. Savings assume a draughty property being fully draught-proofed.
DIY draught-proofing pays for itself within months. Even professional treatment pays back in 2 to 4 years. Beyond the financial return, the comfort improvement is immediate: no more cold draughts across your feet, fewer cold spots near windows, and a more even temperature throughout the house. Use our insulation savings calculator to see how draught-proofing combines with other upgrades.
Draught-proofing before a heat pump
If you are planning a heat pump, draught-proofing is essential preparation. Heat pumps deliver warmth at lower temperatures than gas boilers, which means draughts are more noticeable and more costly. Every £1 spent on draught-proofing reduces the heat pump's workload and your electricity bills permanently.
Combined with loft insulation and cavity wall insulation, draught-proofing can reduce your heat demand by 20 to 30%, allowing a smaller, cheaper heat pump. Use our heat pump calculator to see the impact.
Draught-proofing and ventilation
A well draught-proofed home needs adequate ventilation to prevent condensation and maintain air quality. This is especially important after insulating, as a tighter building envelope traps more moisture indoors.
At a minimum, keep trickle vents on windows open, ensure extractor fans in kitchens and bathrooms work properly, and never block air bricks serving gas appliances or underfloor spaces. If you notice increased condensation on windows after draught-proofing, you may need to improve ventilation rather than reverse the draught-proofing.
For heavily insulated and draught-proofed homes, mechanical ventilation with heat recovery (MVHR) provides fresh air while recovering 90% of the heat that would otherwise be lost through open windows. MVHR systems cost £3,000 to £6,000 installed.
Track your indoor humidity with a recommended digital hygrometer to monitor conditions after draught-proofing. Use our EPC improvement planner to see how draught-proofing affects your rating alongside other improvements. Monitor savings with recommended energy monitors.
Frequently asked questions
How much does draught-proofing cost?
DIY: £30 to £100 for a whole house. Professional: £200 to £400. Sash windows: £80 to £150 per window professionally. See recommended draught excluder strips to get started.
How much does draught-proofing save?
£60 to £125 per year depending on property type and how draughty the home is. Use our calculator for your specific figure.
Where are the biggest draughts in a house?
Suspended timber floors and windows account for 40 to 55% of air leakage. Then doors, chimneys, letterboxes, and pipe penetrations. Check our EPC improvement guide for the full priority order.
Can you draught-proof sash windows?
Yes. Brush pile strip in the sliding channels is the standard fix. DIY kits cost £15 to £30 per window. Professional fitting costs £80 to £150 per window.
Should I draught-proof if I have a gas boiler?
Yes, but never seal ventilation in rooms with gas appliances. Keep air bricks and trickle vents open in those rooms. Seal everything else.
Data sources
Savings data from Energy Saving Trust. Energy prices from Ofgem Q1 2026 price cap. Ventilation guidance from Building Regulations Approved Document F.