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All houses need a supply of fresh air, but over-ventilation in the form of draughts can be undesirable, particularly in cold, windy weather. For many homes, draught-sealing doors, windows and other gaps can be an inexpensive way of improving comfort and reducing heating bills while helping to protect the environment.
The key to applying draught seals to doors and windows is to seal the gap without making the door or window difficult to close. In many cases, a perfect seal is neither practical nor desirable, and it is sufficient to form a seal, which excludes most of the draught.
This section provides an overview of the various types of draught-sealants available, their suitability to various applications and a quick guide to determining whether draught sealing is likely to prove a financially worthwhile exercise. Make sure that you do not over-seal, as inadequate ventilation may result in a stuffy atmosphere and condensation problems and may even pose a safety hazard if the air supply to combustion appliances is insufficient.
In older houses, more than half of the cold outside air entering the house is admitted through the windows and doors. Other sources of draughts include attic hatches, suspended wooden floors, and spaces between window- and door-frames and wall openings. There may also be gaps around pipes
penetrating external walls, floors and ceilings. New windows and doors are generally supplied with draught-seals, but many older units are unsealed. If the opening part of the door or window does not fit tightly against the frame,
draughts can enter or leave through the gap. Large gaps can generally be detected by inspection, and in cold, windy weather, it may be possible to feel a cold draught entering the house. (Bear in mind, though, that cold draughts will enter only on the upwind side of the house. On the downwind side and at the top of the building, warm air will tend to exit through gaps.)
The width of the gap around windows and doors may not be uniform. Gap sizes of up to 8 mm around wood-frame windows and 10 mm for wooden doors are not uncommon.
The larger the gap, the more worthwhile draught sealing is likely to prove.
The main categories of draught-sealing products available are compression and sliding seals, both of which are available in hidden or visible options, and fillers or sealants. Compression or sliding seals are often used for gaps between moving components, for example, the opening part of windows and
doors. Fillers or sealants are generally more convenient for fixed openings, for example, at skirting boards. Examples of each type are illustrated in this leaflet. Some guidance on installing draught stripping is also provided, though manufacturers' instructions should be followed for particular products.
The most common hidden-type compression seal product available is a self-adhesive foam tape. This sometimes comes with a backing that is peeled off as the tape is stuck on to the frame. Surfaces to which the strip is to be applied should be clean and dry. Generally, the strip is applied to the frame stop opposite the closing face of the door/ window. The closing face should compress the foam rather than slide across it and pull it off. If the gap at any part of the opening is too wide to be sealed by one layer of the tape, another may be applied over the first layer. On the other hand, in places where the gap is less than a millimetre or so, no tape should be applied, since it could make the door or window difficult to close.
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