Draught-proofing is the highest-return, lowest-cost energy improvement you can make to almost any UK home. Unlike loft insulation or double glazing, you don’t need planning permission, specialist tools, or a large upfront spend. A weekend and £50–£80 in materials can noticeably cut your heating bills.
Cold air infiltration accounts for roughly 20–30% of heat loss in a typical pre-1980s UK property. Sealing it off does two things: it reduces the energy needed to maintain temperature, and it improves thermal comfort by eliminating cold spots and cold feet.
Where Draughts Actually Come From
Before buying products, a proper survey is worth doing on a cold, breezy day. Run your hand along these areas to feel cold air movement:
- Door frames (especially external doors and loft hatches)
- Window frames and sashes
- Letterboxes and keyholes
- Floorboards and skirting boards (particularly in older homes with suspended timber floors)
- Chimney breasts (whether or not the chimney is in use)
- Electrical sockets and switches on external walls
- Gaps around pipes entering through walls
- The join between walls and ceilings in older properties
A draught of just 1mm around the perimeter of a standard door frame is equivalent to leaving a 15mm diameter hole open — a surprisingly large air leak for such a slender gap.
Products and What They Cost
| Location | Product type | DIY cost | What to look for |
|---|---|---|---|
| External door frames | Self-adhesive foam strip | £4–£8 | E-rated EPDM foam lasts 5+ years |
| External door frames | Brush strip (for heavier-used doors) | £8–£20 | Nylon pile 5–6mm depth |
| Door threshold | Automatic drop seal | £25–£60 | Fits doors 80–90mm wide, adjustable |
| Sash windows | Brush strip to sash channel | £10–£25 per window | Must allow sash to slide freely |
| Casement windows | Compression seal | £6–£15 per window | EPDM rubber; self-adhesive or pinned |
| Letterbox | Draught excluder flap/brush | £8–£18 | Double-flap type blocks wind best |
| Keyhole | Keyhole cover (escutcheon with flap) | £3–£8 | Fits standard 12mm keyhole |
| Floorboards | Specialist floor filler or silicone | £10–£25 | Flexible; caulk the skirting line too |
| Unused chimney | Chimney balloon or draught excluder | £15–£30 | Must be removed before lighting a fire |
| Loft hatch | Compression strip + insulation board | £15–£35 | Loft hatch edges are often neglected |
| Socket back-boxes | Foam gaskets (pack of 10) | £4–£8 | Fit behind socket plate |
Chimney Draughts: The Big Win
An open chimney on a modest house can lose as much heat as leaving a window permanently open. If you don’t use the fireplace, a chimney balloon is the most cost-effective solution. It inflates inside the flue above the opening and can cut annual heating bills by £60–£100 on its own.
Important: chimneys serving a gas appliance must not be blocked. Fit a balloon only in a fully decommissioned flue, and always tie the trailing ribbon to the grate so you see it before accidentally lighting a fire.
If you use the fireplace occasionally, a throat restrictor plate (fitted by a chimney sweep) reduces the chimney cross-section without blocking it entirely. Cost is roughly £80–£150 fitted.
Suspended Timber Floors
Pre-1930 homes typically have suspended timber floors over a ventilated sub-floor void. The floorboards themselves are rarely airtight, and cold air rises through gaps into the room.
DIY options:
- Flexible acrylic or silicone sealant squeezed into gaps between boards (best done on hands and knees with the boards lightly warmed)
- Specialist floor restoration products that fill gaps while remaining flexible
Do not fill the air bricks in the external wall — sub-floor ventilation prevents timber rot. Seal the floor above, not the ventilation below.
Skirting board sealant at the floor–wall joint is a five-minute job that DIYers routinely overlook. Use flexible decorator’s caulk rather than rigid filler to accommodate seasonal movement.
How to Draught-Proof an External Door: Step by Step
- Measure the frame perimeter and check whether the door currently has any strip — weathered foam is worse than nothing as it compresses flat.
- Clean and dry the rebate (the surface the door presses against). Degrease with methylated spirit.
- Apply self-adhesive EPDM foam strip around the top and sides of the door stop (the raised bead the door closes against). Cut clean mitres at the corners with scissors.
- Fit a brush strip to the threshold — either a surface-mounted strip screwed to the door face, or an automatic drop seal if the floor is uneven.
- Check the door closes fully without the draught strip squashing completely flat — slight compression is correct; if the door bounces back, the strip is too thick.
- Fit a letterbox brush or double-flap by removing the existing letterbox plate, slipping the brush insert over the slot, and re-fixing the plate.
Typical time: 45–90 minutes per external door. Total material cost: £25–£50.
Windows
Sash windows are the worst offenders in Victorian and Edwardian homes. A traditional box sash has four separate gaps: top sash against frame, bottom sash against frame, the two sashes against each other (the meeting rail), and the sash channels.
Purpose-made sash window brush strips fit into routed channels and allow the sashes to still slide. This is a precision job — either hire a specialist (£150–£300 per window) or buy a quality DIY kit (£20–£35 per window) and allow several hours.
Casement windows in good condition simply need a compression seal around the rebate. If the frame has warped away from the opening, a window doctor can re-hang it for £80–£150 per window.
What Professional Draught-Proofing Costs
Professional draught-proofers assess the whole property, identify sources, and supply and fit materials. Typical costs:
| Property type | Professional draught-proofing cost |
|---|---|
| 1–2 bed flat | £150–£250 |
| 3 bed semi-detached | £250–£400 |
| 4+ bed detached | £350–£600 |
These figures typically include door and window seals, letterbox and keyhole covers, and chimney draught exclusion. Floor work is usually an extra.
When to Call a Professional
DIY is the right call for the majority of draught-proofing jobs. Get a professional if:
- You have listed building consent restrictions (some materials may need approval)
- You have original sash windows you are nervous about damaging
- You want a whole-house air-tightness test as part of an EnerPHit retrofit
- Draught investigation suggests structural gaps — cracked mortar, failed pointing, or broken seals around window frames embedded in the fabric of the wall
Does Draught-Proofing Cause Condensation?
This is a genuine concern. Sealing a leaky house reduces adventitious (uncontrolled) ventilation, and if there is no controlled ventilation in its place, moisture levels rise. In practice, the risk applies mainly to homes that go from very draughty to very well sealed in one go — rare with basic draught-proofing alone.
Good practice: ensure kitchens and bathrooms retain functional extract ventilation (a fan or trickle vent), and make sure habitable rooms have background ventilation from trickle vents in window frames or Wall vents. Ventilation requirements are covered under Part F of the Building Regulations.
