Ventilation: Approved Document F, Volume 1 — Dwellings

O N L I N E V E R S I O N F1(1) Purge ventilation 1.26 A system for purge ventilation should be provided in each habitable room. 1.27 Purge ventilation should be capable of extracting at least four air changes per hour per room directly to the outside. NOTE: In order to demonstrate compliance with Part O of the Building Regulations it is likely that higher purge ventilation rates than those given in paragraph 1.29 will be required. 1.28 Purge ventilation should be delivered through one of the following means. a. Openings (e.g. windows or doors). b. A mechanical extract ventilation system. 1.29 Where purge ventilation is delivered through openings in a habitable room, the minimum opening areas in Table 1.4 should be achieved. The values in Table 1.4 are based on BS 5925, which assumes all of the following. a. Single-sided ventilation. b. An urban environment. c. A wind speed of 2.1 metres per second (m/s). d. A temperature difference of 3°C between the air inside and outside the building. 1.30 Depending on the dwelling design or the external climate, it may be possible in certain circumstances to achieve four air changes per hour with smaller openings. If smaller openings than those given in Table 1.4 are specified, expert advice should be sought to ensure that the design complies with requirement F1(1). Table 1.4 Purge ventilation openings Opening type Minimum total area of openings Hinged or pivot windows with an opening angle of 15 to 30 degrees 1/10 of the floor area of the room Hinged or pivot windows with an opening angle of greater than or 1/20 of the floor area of the room equal to 30 degrees Opening sash windows External doors 1.31 Hinged or pivot windows with an opening angle of less than 15 degrees are not suitable for purge ventilation. Performance testing 1.32 The air flow resistance of all components should be considered when specifying ventilation systems. The complete assembly, as installed, should be designed to meet the performance standards of this approved document. The performance of the separate components should be measured according to the relevant parts of BS EN 13141 and other relevant standards. The relevant test standards for common equipment types are given in Table 1.5. 11 Building Regulations 2010 Approved Document F Volume 1, 2021 edition O N L I N E V E R S I O N