Draught-Proofing Your Home: Doors, Windows and the Gaps You Can't See

A draught is warm air you have paid to heat slipping out of the house, replaced by cold air you now have to heat again. In many older homes, gaps around doors, windows, floorboards and fittings add up to the equivalent of a permanently open window. Sealing them is one of the cheapest home improvements there is: most materials cost little, the work rarely needs special skills, and the result is a warmer home that needs less heating.

This guide explains how to find draughts, how to seal each type of gap, and — just as important — where ventilation must be kept open for health and safety.

Why draught-proofing matters

Uncontrolled air leakage has several costs:

• Higher heating bills, because warm air escapes and cold air enters.
• Cold spots and discomfort, even when the thermostat says the room is warm.
• Noise and dust coming in from outside.

Energy-advice organisations generally regard draught-proofing as one of the most cost-effective measures for older, leaky homes, with materials that often pay for themselves quickly through lower bills. Modern, well-sealed homes will see less benefit, but even they can have problem spots.

Draught-proofing versus ventilation

Before starting, it is vital to understand the difference between draughts, which are uncontrolled gaps, and ventilation, which is controlled airflow that a home needs.

Homes need fresh air to remove moisture, cooking smells and pollutants, and fuel-burning appliances need air to burn safely. Never block:

• Air bricks and wall vents.
• Trickle vents in window frames (these can be closed in very cold weather if designed to be, but should not be sealed permanently).
• Extractor fans in kitchens and bathrooms.
• Vents in rooms with open fires, gas fires, boilers or other fuel-burning appliances.
• Under-floor vents that keep timber floors dry.

Blocking ventilation can cause condensation, mould and, in rooms with combustion appliances, a dangerous build-up of carbon monoxide. If you have fuel-burning appliances, make sure a working carbon monoxide alarm is fitted and appliances are serviced by a qualified engineer.

Finding the draughts

Some draughts are obvious. Others need a little detective work.

• Feel for them. On a windy, cold day, move the back of your hand slowly around window frames, door edges, skirting boards, floorboards, loft hatches, letterboxes and pipe openings.
• Use a candle or incense stick — carefully and away from curtains — and watch for the flame or smoke to flicker sideways near a gap.
• Look for light. At night, with a light on in the room, gaps around external doors may show light from outside, or vice versa.
• Check for dust trails on carpets near skirting boards, which can indicate airflow.

Make a list of each draught you find; it becomes your shopping list.

Doors

External doors are often the worst offenders.

• Gaps around the frame. Fit self-adhesive foam strips, rubber "P" or "E" profile seals, or brush strips to the frame so the door compresses them when closed. Choose a thickness that seals the gap without making the door hard to close.
• Gap at the bottom. Fit a brush strip or a rubber sweep to the bottom of the door, or a threshold seal. A fabric "draught snake" laid along the bottom is a simple, cheap option for internal doors.
• Letterboxes. A letterbox brush or flap fitted on the inside stops a surprising amount of cold air.
• Keyholes. A keyhole cover with a swinging flap costs very little.
• Internal doors. Draught-proofing internal doors is generally less important, but closing doors to unheated rooms keeps warmth where you need it.

Windows

• Opening windows. Self-adhesive foam or rubber strips fitted where the opening part meets the frame seal gaps when the window is shut.
• Sash windows. These are often very draughty. Specialist brush seals and parting-bead seals are available; for period windows, specialist draught-proofing services can fit discreet seals that keep the window working.
• Gaps between frame and wall. Fill with a suitable flexible sealant (silicone or decorator's caulk, depending on location) after cleaning the surfaces.
• Secondary glazing film — a clear film stretched over the window frame and tightened with a hairdryer — is an inexpensive, temporary option for rarely opened windows, adding an insulating layer of air.
• Heavy curtains close the gap at night.

Floors and skirting boards

Gaps between bare floorboards and between floors and skirting boards let cold air in from below, particularly in older homes with suspended timber floors.

• Floorboard gaps can be filled with flexible fillers designed for floors, or with thin strips of wood glued into larger gaps. Some products are pushed into the gap like a rope.
• Skirting board gaps can be sealed with flexible sealant.
• Rugs and carpets with underlay reduce draughts and make floors feel warmer.

Remember that suspended timber floors rely on ventilation underneath to stay dry; seal the gaps in the room, not the vents in the outside walls below.

Loft hatches

Warm air rises, and a loft hatch without seals is effectively a hole in the ceiling. Fit foam strips around the frame so the hatch presses against them, and add a layer of insulation board to the top of the hatch itself.

Chimneys and fireplaces

An unused open chimney can draw a large amount of warm air out of a room.

• Chimney balloons or chimney sheep (woollen plugs) block the flue while allowing a small amount of ventilation. They must be removed before lighting a fire, and many come with a warning label for this reason.
• Fireplace covers close the opening.
• A capped chimney may still need some ventilation to prevent damp; follow the product instructions and seek professional advice if unsure.

Never block a chimney or flue that serves a working fire, stove or boiler.

Pipes, cables and fittings

Wherever a pipe, cable or wire passes through a wall or floor — under sinks, behind toilets, around boilers — there may be a gap.

• Small gaps can be filled with flexible sealant.
• Larger gaps can be filled with expanding foam, used carefully according to its instructions and away from heat sources.
• Electrical sockets and switches on external walls sometimes leak air; foam gaskets designed for this purpose can be fitted behind the faceplates, but any electrical work should be done with the power safely isolated, and if you are not confident, by a qualified electrician.

Choosing materials

Cheaper foam strips can wear out within a few years; rubber and brush seals generally last longer. Spending slightly more on durable materials for frequently used doors and windows is often worthwhile.

Doing it yourself or calling a professional

Most draught-proofing is well within the abilities of a careful DIYer. Professional help is sensible for:

• Period sash windows, where poor workmanship can stop windows opening.
• Homes with fuel-burning appliances, where ventilation requirements must be checked.
• Rented homes, where you should agree changes with your landlord first. Many removable measures — draught snakes, letterbox brushes, chimney balloons — do not need permission.
• Any work involving electrical fittings, unless you are competent and the power is isolated.

Checking the results

On the next cold, windy day, repeat the hand or candle test around the areas you treated. You should notice fewer cold spots and that rooms reach a comfortable temperature faster. If condensation becomes a problem after draught-proofing, increase ventilation — use extractor fans, open windows briefly each day, and make sure vents are clear.

Common mistakes to avoid

Draught-proofing is simple, but a few errors come up again and again:

• Buying the wrong thickness of seal. A strip that is too thick stops doors and windows closing properly, and people then rip it off. Measure the gap with a coin or a strip of card before buying, and choose a seal that compresses slightly.
• Fitting strips to dirty or damp surfaces. Self-adhesive products fail quickly if surfaces are greasy or wet. Clean with soapy water, let everything dry, and fit them on a mild day if possible.
• Sealing over paint that is still soft. Fresh paint can stick to seals and tear when the door or window opens.
• Forgetting the hinge side of the door. Draughts often come in along the hinge side as well as the opening edge.
• Blocking trickle vents or air bricks to "finish the job". These are ventilation, not draughts, and are there for a reason.
• Using expanding foam near heat sources or electrics. Follow the product instructions and keep foam away from flues, boilers and wiring.

Draught-proofing in rented homes

Tenants can do a great deal without making permanent changes. Draught snakes, letterbox brushes, keyhole covers, removable window film, thick curtains, rugs and chimney balloons can all be taken away at the end of a tenancy. For fixed changes, such as new seals or sealant around frames, ask your landlord first; many are happy to agree because draught-proofing protects the property from damp and makes it easier to let.

A weekend draught-proofing plan

1. Saturday morning: walk through the home and list every draught.
2. Saturday afternoon: buy materials for the worst offenders — usually the front door, letterbox and the draughtiest windows.
3. Sunday: fit door seals and letterbox brush, seal window frames, add a loft hatch seal, and fill obvious gaps around pipes.
4. The following weekend: tackle floorboards, skirting boards and the chimney.

The bottom line

Draught-proofing is unglamorous, inexpensive and remarkably effective in leaky homes. Find the gaps, seal them with the right materials, and keep essential ventilation clear. The result is a warmer, quieter, more comfortable home — and a heating system that no longer has to warm the street outside.