Roof Space Ventilation

Roof space ventilation can reduce the cooling load of your dwelling by allowing hot air and excess moisture in the roof space to escape.

Roof space ventilation can only be applied to a pitched roof with a flat ceiling. If the roof space is ventilated, the minimum number of ventilators will be displayed on the BASIX certificate. Ventilators should be installed in locations that optimise the ventilation in the roof space. 

BASIX recognises 3 types of roof space ventilation which must be installed in accordance with the following requirements:

Gable-end vents

• Gable-ends are the triangular part of a wall adjacent to the roofspace in a pitched roof.
• This option will require a minimum of two vents, one at each end of the roofspace, with an aggregate fixed open area of not less than 1% of the ceiling area.

Wind-driven ventilators (whirligigs)

• This is a passive vent that relies on air pressure differences to operate. This option will require one ventilator for every 100 m² of ceiling (or part thereof), and eave or gable-end vents with an aggregate fixed open area of not less than 0.2% of the ceiling area.

Powered roof ventilators

• Powered roof ventilators are a mechanical system that uses a fan to push hot air out of the roof space, creating a more effective ventilation system. Many powered vents have automatic sensors that activate the fan based on roof space temperature.