Venting A Cold Flat Roof With Parapet Walls

A cold roof is where all of the insulation is placed either between and under or completely under the joists or deck.

Venting a cold flat roof with parapet walls.

Originally published may 1976. When thermal insulation is placed below the deck the ventilation must. Cold roofs by the way are not recommended for high humidity areas see the blog on how to insulate. It is supplied with pre drilled fixing holes and an integral insect resistant grille.

Each unit is 1 2 metres in length and the heavy duty profile incorporates an integral pivothold hinge. On the unventilated side there is no overhang just a solid facia board flush with the wall. 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. What is flat roof ventilation.

The rav fl promotes air entry where a flat roof abuts a vertical masonry wall. No insulation is on top. A cold roof system sees the insulation placed immediately above the ceiling between the joists with ventilation space above the insulation. You only need ventilation in a cold roof.

In this way the roof itself is kept cold. Venting of flat roofs. The disadvantage of this method is wasteful cutting of insulation to install between the joists labour required to install the material and increased electrical cables required to prevent overheating that run within the insulation. 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.

There are two types of flat roof systems warm and cold roofs which affect the positioning of the ventilation. Used to provide ventilation where flat roofs abut masonry. I have a cold flat roof ventilated by soffit vents on one side and no ventilation on the other side. Vparawallcr ventilated parapet detail cold roof installation of a typical ventilated parapet detail with the dryseal flat roofing system on a cold roof construction.

The 25mm batten space creates a clear airpath to the roof void below so reducing the possibility of condensation and mould growth.