NEW APPROVED DOCUMENT F, VOLUMES 1 AND 2

Approved Document F (Ventilation) – Effective 15/06/2022

Replacing windows

General

When building work is carried out on an existing dwelling that will affect ventilation for example replacing a window or door, the ventilation of the dwelling should either meet the standards detailed in Approved Document ADF 1 or be not less satisfactory than before the work was carried out.

Note.  Ventilation through infiltration (draughty windows/doors) should be considered to be part of the ventilation system of a dwelling. Reducing infiltration might reduce the indoor air quality of the dwelling.

Existing windows with background ventilators

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.

1. Not be smaller than the background ventilators in the original window.

2. 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. (See below paragraph)

Existing windows without background ventilators

Replacing the windows is likely to increase the airtightness of the dwelling. If ventilation is not provided via a mechanical ventilation heat 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.

1. incorporating background ventilators on the replacement windows equivalent to the following.

2. Habitable rooms – minimum 8000mm² equivalent area.

3. Kitchen – minimum 8000mm² equivalent area.

• Bathroom (with or without a toilet) – 4000mm² equivalent area.

1. If the dwelling will have continuous mechanical extract ventilation, installing background ventilators in any replacement windows which are not in wet rooms, with a minimum equivalent area of 4000mm² in each habitable room.

2. 1. The risk of draughts.

   2. Security issues.

   3. The difficulty of measuring the equivalent area.  Other ventilation provisions, if it can be demonstrated to a building control body that they comply with 3.2.