How to Draught-Proof Doors and Windows UK

Find the draught before sealing it

Start by identifying where moving air is actually entering. On a cold or windy day, check around window frames, external doors, letterboxes, keyholes and the bottom edge of doors. Visible light around a closed frame, rattling windows, whistling sounds or curtains moving when the window is shut can all point to unwanted gaps.

Draughts are different from intentional ventilation. An accidental gap around a frame can waste heat, while a trickle vent or wall vent is there to manage fresh air and moisture.

If the room feels cold even after obvious draughts are controlled, work through the broader checklist in How to Stop Heat Loss in a Room UK.

How to draught-proof windows

Opening casement windows

For windows that open, draught-proofing strips are fitted around the frame so the closing window compresses or meets the seal. The strip needs to be thick enough to close the gap without making the window difficult to shut.

• Self-adhesive foam strips: inexpensive and easy to fit, but they may wear out sooner.
• Brush or wiper strips: usually more durable and useful where surfaces move against one another.
• Silicone sealant: suitable for fixed cracks or gaps that do not need to move.

If the strip is too thin, air can still pass through. If it is too thick, the window may not close properly, so measure the gap rather than choosing the largest seal available.

Sliding sash windows

Sliding sash windows need to move vertically, so ordinary foam strips are often a poor fit. Brush seals are generally more suitable because they reduce airflow while allowing the sash to slide. Older or valuable timber windows may be better handled by a specialist if the gaps are irregular or repairs are also needed.

Windows that do not open

If a fixed window has a small crack between the frame and surrounding material, an appropriate sealant can close the unwanted gap. Do not seal drainage paths or ventilation features built into the window system.

How to draught-proof external doors

External doors can leak air around several separate points, so one product does not always solve the whole problem.

Around the frame

Compression, foam or wiper seals can close gaps between the door and frame. The door should still latch normally and the seal should make contact without being crushed excessively.

Under the door

If there is a gap beneath the door, a brush strip, flexible blade seal or properly fitted threshold seal can reduce airflow. Choose a type that suits the floor surface and still lets the door open freely.

Letterboxes and keyholes

Letterboxes can benefit from purpose-made brushes or flaps. Traditional keyholes can use a simple escutcheon or swinging cover to reduce direct airflow.

What you should not seal

Draught-proofing should target uncontrolled gaps, not intentional ventilation. Energy Saving Trust advises keeping designed ventilation available because it helps control moisture, condensation and indoor air quality.

• Do not block trickle vents above or within windows.
• Do not cover wall vents or ventilation grilles that are intended to provide fresh air.
• Do not seal ventilation needed for open-flue or flueless gas appliances.
• Do not block extractor routes in kitchens, bathrooms or utility rooms.
• Take extra care around open fires and chimneys; only use an appropriate removable chimney draught solution when the fireplace is not in use and it is safe to do so.

For a warmer bedroom, see How to Keep a Bedroom Warm Without Central Heating UK, which combines heat-loss control with safe ventilation and targeted heating.

How much does draught-proofing cost, and what can it save?

DIY draught-proofing can be inexpensive when the problem is limited to a few simple gaps. Professional work costs more but may be worthwhile when several windows or doors need adjustment, seals are difficult to fit, or the frames themselves need repair.

Energy Saving Trust currently estimates that professional draught-proofing of windows and doors can cost around £250 for a whole house. It also estimates that draught-proofing windows, floors and doors could save around £55 a year in Great Britain. These are broad household estimates rather than guaranteed savings: the actual result depends on the size and condition of the property, the number of gaps, heating habits and energy prices.

The comfort benefit can be just as important as the bill saving. A room with fewer cold draughts may feel comfortable at a lower thermostat setting or with shorter periods of heating.

Should you draught-proof doors and windows yourself?

Simple adhesive seals, brush strips and keyhole covers are usually straightforward DIY jobs if the frames are sound and you can identify the gap clearly. More complex work may need a professional.

DIY is usually reasonable when:

• the frame is in good condition;
• the gap is small and consistent;
• you can fit a removable or replaceable seal without altering the window or door structure;
• you are certain you are not blocking designed ventilation.

Consider professional help when:

• windows or doors are warped, rotten or difficult to close;
• large or irregular gaps suggest an installation or structural problem;
• you have sliding sash, listed or heritage windows that need specialist treatment;
• the home already has condensation or ventilation problems;
• you are unsure about ventilation requirements around gas or solid-fuel appliances.

What type of draught excluder should you choose?

The best product depends on the gap rather than on a single brand or material. Foam is useful for simple low-cost jobs, brush seals work well on moving surfaces, flexible blade seals can suit door bottoms, and silicone is useful for fixed cracks.

For product selection, compare specific seal types, durability and fit in our Best Draught Excluders UK guide. This article remains the installation and decision-making foundation.