Last edited 10 Jul 2018

Draught proofing buildings

A draught is a noticeable current of air inside a building that can make its occupants uncomfortable and result in unnecessary heat loss. Draught proofing, also known as draught exclusion, is a technique for controlling draughts. It can be an inexpensive and effective way of improving thermal comfort and energy efficiency.

The locations of draughts are easiest to identify on windy days, by wetting the back of a hand and passing it over the area most likely to be affected – around window frames, doors, pipes, etc. A building should be closely inspected for any unwanted gaps and uncovered openings to the exterior such as keyholes, letterboxes, chimneys, floorboards, skirting boards, loft hatches, fireplaces, wall cracks, fittings, and so on.

Draughts can also be caused by air falling rapidly when it comes into contact with a cold surface such as a window.

Single-glazed windows, particularly sash windows, can be prone to draughts. The most obvious method for draught proofing windows is to install double glazing. However, if this isn’t an option or is too expensive, there are more cost-effective alternatives:

Window foam seal: A thick tape which is easy to apply. This isn’t the best method for sliding sash windows.
Foam sealant: Can be sprayed into gaps around windows and doors.
Metallic or plastic brush strips: More expensive than foam or tape but more durable.
Cling film: A cling film sheet taped around a window, leaving a gap of a few millimetres, and heated with a hairdryer until taut. A cheap and simple solution although it may not be entirely affective.

Draughts are also common from gaps under external doors as well as the letterbox and keyholes. Draught proofing techniques that can be effective for doors include:

Fitting a weatherbar or door brush strip which act as a seal at the bottom of the closed door.
Fitting a draught excluder to the bottom of the door or letterbox.
Letterbox plates can prevent cold air entering.
Keyhole covers can prevent cold air entering and slide out of the way of keys.

Where pipes enter a building, small gaps can be treated with silicone filler, and larger gaps may require expanding polyurethane foam.

Draughts that are found in wall cracks can be prevented by filling the cracks with cement or hard-setting fillers. If cracks persistently appear in the same area they may require a professional to address the underlying problem.

Draughts from redundant extractor fans can be prevented by filling the fan outlet with bricks and/or concrete and then sealing it. Similarly, draughts from chimneys and fireplaces can be stopped by fitting a cap over the chimney pot or fitting a chimney draught excluder. Care must be taken not to completely seal chimneys, ad they need some ventilation to prevent moisture build up.