Airtightness and ventilation
The airtightness of the house determines how much air leaks into and out of the dwelling. In very leaky houses heat losses due to air infiltration can account for a third to a half of the total heat lost. Leaky houses also have lots of draughts leading to them being costly to run and uncomfortable to live in. Ventilation of the dwelling is desirable and necessary to remove moisture and other pollutants from the air. Ventilation should be provided by controllable openings, such as trickle vents or mechanical extract fans.
It is important to remember that rooms with open-flue appliances, such as gas fires, require a direct supply of fresh air for the safe operation of the appliance. A separate provision should be made as close as possible to the appliance.
Airtightness
Some simple measures can be taken to improve the airtightness characteristics of the house. Draught proofing around windows, doors and the loft hatch; sealing around service pipes which pass thorough floors, walls and roofs; block up unused chimneys, but include ventilation to the room by means of a ventilator, if relaying carpets use underlay or sheet flooring materials below the carpet.
Ventilation
Controlled ventilation is necessary to provide a healthy internal environment, but should be provided in an energy efficient way. Ventilation can be provided by mechanical fans or passive systems that rely on the natural buoyancy of warm air to remove moisture. A ventilation strategy should include a means to provide background ventilation for example, trickle vents in windows (a small slot in the window frame with a closable cover that allows a flow of fresh air to the room), a means to rapidly ventilate a room, such as an openable window to quickly remove odours or air a room, and final a means of extracting warm, moist air from kitchens and bathrooms to reduce the risk of condensation forming. The Building Regulations, Part F specifies the minimum amount of ventilation that should be provided in a new building.
Further Information
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