Venting A Cold Flat Roof With Parapet Walls

A cold roof system sees the insulation placed immediately above the ceiling between the joists with ventilation space above the insulation.

Venting a cold flat roof with parapet walls.

Originally published may 1976. Where there is a parapet or an external wall abutment to the flat roof the fv250 ventilator can be used above a 150mm timber upstand battened off the wall by 25mm as shown below. There are two types of flat roof systems warm and cold roofs which affect the positioning of the ventilation. Cold roofs by the way are not recommended for high humidity areas see the blog on how to insulate.

Diagram below explains the build up. Used to provide ventilation where flat roofs abut masonry. A cold roof is where all of the insulation is placed either between and under or completely under the joists or deck. I have a cold flat roof ventilated by soffit vents on one side and no ventilation on the other side.

No insulation is on top. The rav fl promotes air entry where a flat roof abuts a vertical masonry wall. Each unit is 1 2 metres in length and the heavy duty profile incorporates an integral pivothold hinge. Venting in building construction as a technique of cooling by air flow and of controlling or removing moisture has been in use for many years.

What is flat roof ventilation. On the unventilated side there is no overhang just a solid facia board flush with the wall. The 25mm batten space creates a clear airpath to the roof void below so reducing the possibility of condensation and mould growth. Venting of flat roofs.

You only need ventilation in a cold roof. Flat roof ventilation allows for the circulation of air in the property particularly for warmer rooms in residential buildings. In this way the roof itself is kept cold. It is supplied with pre drilled fixing holes and an integral insect resistant grille.

How do i add ventilation on this side to create through air movement.