Appendix A – Ventilation guidance

All habitable rooms must have an opening window, equivalent to 1/20th of the floor area, to the outside air to provide adequate ventilation. French or patio doors that have no separate openable casements, or where there is no alternative openable casement within the room, are not considered acceptable in bedrooms.

Windows and doors

(1) Double glazed windows and doors

Double glazed windows and doors should comply with the current Building Regulations Part L.

(2) Secondary glazing

A proprietary secondary glazing system set in an aluminium or plastic frame shall be installed in accordance with the manufacturer’s instructions.

The air gap between the existing and secondary glazing shall be a minimum of 20mm. Secondary glazing shall be draught stripped while the existing windows shall be left without seals.

The selected system should be easily openable for rapid ventilation and be capable of being left slightly open to allow trickle ventilation into the room.

(3) Skylights/roof casements (such as Velux)

If skylights/roof casements are the only source of light and/or ventilation within a habitable room, they must meet all of the following requirements;

  • the skylight/roof casement must be able to be fully opened for ventilation during spells of prolonged and heavy rain or snow without allowing it to enter the room;
  • the skylight/roof casement must have integral passive ventilation for ventilation even when the window is shut; and
  • the skylight/roof casement must provide a reasonable view for the occupant(s). The Housing Health and Safety Rating System (HHSRS) states as a relevant matter that there should be a “reasonable view out of all rooms, other than those where privacy is required, such as bathrooms and WCs”, as this can have a negative effect on the mental health of the occupants, especially over the longer-term

The case officer will ultimately determine whether or not the skylight/roof casement is suitable and meets all of the requirements above. In instances where it is not considered suitable, alternative windows will be required to be installed and may be included within stipulated conditions on an HMO licence.

(4) Draught proofing – general

Proprietary draught strips should comply with BS 7386: 1997 and installation shall be in accordance with BS Code of Practice 7880: 1997 and manufacturer’s instructions.

(5) Draught proofing external doors

Suitable draught strips for the top and sides of the door shall be good quality rubber (EPDM, silicone), sheathed foam or nylon brush, with rigid PVC-U or aluminium carriers nailed or screwed to the door frame. Seals fitted within the gap between the door and frame shall have a range of 6mm with a compression allowance of 3mm.

A letter box draught cover and aluminium threshold seal incorporating flexible draught and weather strips should also be provided.

(6) Draught proofing wooden windows

Where applicable, draught strips shall be angled blade seals or rubber tube fixed to carriers for casement windows and brush pile bonded to carriers for sliding sash windows. Self-adhesive options should be avoided where possible. Ensure that the strips are suitably sized for the gaps to be covered.

(7) Draught proofing steel framed windows

Specialist draught strips may be needed for these windows as they often have very small gaps, especially on the hinge side. These include tube and ‘V’ seals, fixed face seals and clip on seals where a carrier is fitted into position over the thin steel section of the frame.

(8) French and patio doors

French or patio doors as the only source of ventilation within a bedroom is not acceptable and all bedrooms must be provided with adequate openable window casements that allow for appropriate ventilation. This should provide a minimum openable area of 1/20th of the total floor area.