Last edited 16 Jun 2018

Draught proofing buildings

See also: Draughts in buildings.

Draught proofing, also known as draught exclusion, is a means of controlling and preventing the leakage of cold air inside a building. A draught occurs when cold damp air penetrates the building fabric, displacing the warmer internal air. It can result in unnecessary heat loss and thermal discomfort. Draught proofing is an inexpensive and effective way to improve the thermal comfort of a building as well as its 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. – as this should detect the change in temperature. 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, around electrical fittings, and so on.

To some extent draughts are unavoidable as its not desirable to completely seal a building as part of the insulation process. Ventilation is important in areas such as the kitchen, bathroom and where there are open fires or flues.

Single-glazed windows, particularly sash windows, can often 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 are 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. Cheap and simple solution although 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 or lead up a loft, draughts can often be found. 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 it may require a professional to address the problem.

Draughts from old 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.

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