Uncontrolled ventilation, also referred to as air leakage, is a major source of heat loss. Draught-proofing is recognised as being one of the most cost-effective solutions that reduces energy use, improves occupant comfort and has little change to the building’s appearance. It is effective in controlling the amount of unintended movement of air, as this impacts overall heat loss and air leakage. For example, Historic England’s research has suggested draught-proofing windows can reduce air leakage from by between 33% and 50%. This substantially reduces the heating requirement needed for the effected space. If the building is an exposed timber-framed building, ensuring there are no gaps between the frame and the infill panels will also have a significant effect. Materials used to fill the gaps will need to be appropriate for the building. Details and diagrams pertaining to draft proofing are available in Historic England’s Guidance Traditional Windows: Their Care, Repair an Upgrading.
Controlling ventilation in a building can reduce heat loss, as well as provide solutions for cross ventilation in the summer months, when there can be concerns of over-heating. For example, temporarily blocking unused chimney flues with a flue balloon in colder months and removing it in warmer months to encourage the flow of air when needed.
Controlling air leakage is different from ventilation. Ventilation is still required and is important for moisture control and occupant health. Any intended ventilation, such as extractor fans and air bricks, should not be sealed up.
Further information on draughtproofing and ventilation
Historic England’s Draught-proofing windows and doors
Historic England’s Open fires, chimneys and flues
Energy Saving Trust guidance on draught-proofing
Historic Environment Scotland’s Ventilation in Traditional House
Page updated: 10/07/2023