Technical Support - Flat Roofing

What is Flat Roof Ventilation?

Flat roof ventilation allows for the circulation of air. The positioning of the ventilation depends on whether it is a cold or warm roof. When thermal insulation is used ventilation must also be on the underside. A warm flat roof usually does not require ventilation.

What space do I need to allow for the ventilation?

To ensure sufficient ventilation, enough space must be provided to allow for the movement of air, preventing the risk of condensation forming within the roof. Building regulations state that a ventilation gap of at least 50mm must be in place between the insulation and the underside of the flat roof deck.

Do I need a Vapour Control Layer?

A vapour control layer must be installed for both types of roofs. On a warm flat roof, the layer is installed underneath the insulation to stop moisture interacting with it through rising thermal pressure lower down in the building. For cold flat roofs, the vapour layer needs to be positioned underneath the insulation layer.

I need to ventilate my cold flat roof, what can I use?

We provide a range of Flavent Ventilation Outlets, also known as Breather Vents, which are ideal for ventilation of a cold flat roof (also suitable on warm roofs if required). They come in a range from 70mm, 100mm and 125mm diameters with hard PVC, bituminous or our ingenious screw connector flanges to allow installation into most flat roof finishes.