Adequate ventilation removes excess moisture that can contribute to condensation and pollutants. Inappropriate and or inadequate ventilation can contribute to the hazards damp and mould, excess cold, excess heat and pollutants.
The dwelling should be able to cope with normal occupant activities that may produce excess moisture, without persistently high relative humidity. There should be provision for the safe removal of moisture-laden air during peak production. This should include extraction during cooking or bathing, either by mechanical means, passive stack ventilation, or a combination of both, and direct venting of clothes drying facilities (whether tumble driers or drying cabinets) to the exterior.
There should be sufficient and appropriate means of ventilation to deal with moisture generated by normal domestic activities without the need to open windows. Opening windows can result in heat loss, noise, and may be a security risk. Provision for background ventilation may be necessary via trickle vents in replacement windows, insertion of high-level airbricks, or by a passive stack or a MHRV system.
Such hazards can be reduced or eliminated as follows:
Kitchens and bathrooms:
- Mechanical extract ventilation should be provided in kitchens and bathrooms in accordance with Approved Document F of the Building Regulations.
- By the provision of mechanical extract ventilation that is automatically controlled with a humidistat switch or a minimum 15 minute overrun facility; fans should be wired to the lighting switch and be capable of giving a minimum of 4 air changes per hour. The minimum extraction rate is 60 litres of air per second for kitchens and 15 litres per second for bathrooms.
- Mechanical ventilation MUST be provided in bathrooms and kitchens where there is no natural ventilation. By the provision of background ventilation to window frames (trickle vents) or external walls (air bricks) with an area of 8000mm². All such vents must be controllable by the occupier.
Living rooms and bedrooms:
- Rapid ventilation, i.e. opening windows must have openings of no less than 1/20th of the floor area.
- Background ventilation to window frames (trickle vents) or external walls (air bricks) with an area of 8000mm². All such vents must be controllable by the occupier.
- In habitable rooms where the ventilation is naturally restricted (e.g. basements), a minimum floor to ceiling height of 2.13m (7ft) is required. In all habitable rooms the opening window and other ventilation openings should normally extend to 1.75m above the floor level.