Ventilation: Approved Document F, Volume 1 — Dwellings

F1(1) O N L I N E V E R S I O N 3.11 If the method in Diagram 3.1 results in the work being categorised as Category B, it is likely that the ventilation provision of the dwelling has been reduced below the requirements of F1(1). Further ventilation provision should be provided by one of the following means. a. Natural ventilation, by following the system-specific guidance in paragraphs 1.47 to 1.59. It is assumed that any existing purpose-built ventilators are in working order and that the equivalent area has not been compromised. b. Continuous mechanical extract ventilation, by following the system-specific guidance in paragraphs 1.60 to 1.66. c. Mechanical ventilation with heat recovery, by following the system-specific guidance in paragraphs 1.67 to 1.73. To avoid unintended air pathways, existing background ventilators should be covered or sealed shut. 3.12 If the method in Diagram 3.1 results in the work being categorised as Category C, it is likely that the ventilation provision of the dwelling has been reduced significantly below the requirements of F1(1). Further ventilation should be provided by one of the following means. a. Natural ventilation, by following expert advice for the design, sizing and positioning of ventilators to ensure adequate ventilation provision. b. Continuous mechanical extract ventilation, by following the system-specific guidance in paragraphs 1.60 to 1.66. c. Mechanical ventilation with heat recovery, by following the system-specific guidance in paragraphs 1.67 to 1.73. To avoid unintended air pathways, existing background ventilators should be covered or sealed shut. 3.13 Appendix D provides a checklist for determining the ventilation provision in an existing dwelling. It may be used before energy efficiency measures are carried out to establish whether an existing dwelling complies with the requirement for adequate means of ventilation. Replacing windows Existing windows with background ventilators 3.14 If the existing windows have background ventilators, the replacement windows should include background ventilators. The new background ventilators should comply with both of the following conditions. a. Not be smaller than the background ventilators in the original window. b. Be controllable either automatically or by the occupant. If the size of the background ventilators in the existing window is not known, the ventilator sizes in paragraph 3.15 may be applied. Existing windows without background ventilators 3.15 Replacing the windows is likely to increase the airtightness of the dwelling. If ventilation is not provided via a mechanical ventilation with heat recovery system, then increasing the airtightness of the building may reduce beneficial ventilation in the building. In these circumstances, it is necessary to ensure that the ventilation provision in the dwelling is no worse than it was before the work was carried out. This may be demonstrated in any of the following ways. 24 Approved Document F Volume 1, 2021 edition Building Regulations 2010 O N L I N E V E R S I O N