Ventilation: Approved Document F, Volume 1 — Dwellings

A O N L I N E V E R S I O N Appendix A: Key terms Except for the items marked * (which are from the Continuous mechanical extract ventilation Building Regulations 2010), these definitions apply Mechanically driven ventilation that continuously only to Approved Document F, Volume 1: Dwellings. extracts indoor air and discharges it to the outside. Air permeability The measure of airtightness of Continuous operation Uninterrupted running of a the building fabric. It is defined as the air leakage mechanical ventilation device, such as continuous rate per hour per m2 of envelope area at the test mechanical extract ventilation or mechanical reference pressure differential of 50Pa or 4Pa. ventilation with heat recovery. The air flow rate provided by mechanical ventilation need not be Airtightness The resistance of the building constant but may be varied, under either manual or envelope to infiltration when ventilators are closed. automatic control, in response to the demand for The greater the airtightness at a given pressure the removal of pollutants or water vapour. difference across the envelope, the lower the infiltration. Dwelling A self-contained unit designed to accommodate a single household. Automatic controls A system whereby a ventilation device is adjusted by a mechanical or electronic Equivalent area A measure of the aerodynamic controller that responds to a relevant stimulus. That performance of a ventilator. It is the area of a sharp- stimulus usually relates to the humidity of the air in edged circular orifice through which air would pass a room, pollutant levels, occupancy of the space or at the same volume flow rate, under an identical pressure difference across the device. applied pressure difference, as through the opening under consideration. The equivalent area of a Background ventilator A small ventilation opening background ventilator is determined at 1Pa pressure designed to provide controllable whole dwelling difference in accordance with Table 1.7. ventilation. Expert advice Advice from a suitably qualified Basement (in relation to a dwelling) A dwelling or a competent person. Examples from the ventilation usable part of a dwelling (i.e. a habitable room) that industry of a person competent to give expert is partly or entirely below ground level. Note that advice include a chartered or professional engineer, a cellar is distinct from a basement, in that a cellar a building services specialist, a specialist ventilation is used only for storage, heating plant or purposes manufacturer or members of professional trade other than habitation. bodies. Bathroom A room that contains a bath or Extract ventilation The removal of air directly shower and which can also include sanitary from an internal space or spaces to the outside. accommodation. Extract ventilation may be by natural means or by Building control body A local authority or an mechanical means (e.g. by an extract fan or a central approved inspector. system). Free area The geometric open area of a ventilator. Habitable room A room used for dwelling purposes but which is not solely a kitchen, utility room, bathroom, cellar or sanitary accommodation. 36 Approved Document F Volume 1, 2021 edition Building Regulations 2010 O N L I N E V E R S I O N