Venting A Cold Flat Roof With Parapet Walls

No insulation is on top.

Venting a cold flat roof with parapet walls.

Vparawallcr ventilated parapet detail cold roof installation of a typical ventilated parapet detail with the dryseal flat roofing system on a cold roof construction. 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. Flat roof ventilation allows for the circulation of air in the property particularly for warmer rooms in residential buildings. There are two types of flat roof systems warm and cold roofs which affect the positioning of the ventilation.

The rav fl promotes air entry where a flat roof abuts a vertical masonry wall. Originally published may 1976. 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.

A cold roof is where all of the insulation is placed either between and under or completely under the joists or deck. You only need ventilation in a cold roof. Diagram below explains the build up. On the unventilated side there is no overhang just a solid facia board flush with the wall.

Each unit is 1 2 metres in length and the heavy duty profile incorporates an integral pivothold hinge. When thermal insulation is placed below the deck the ventilation must. The 25mm batten space creates a clear airpath to the roof void below so reducing the possibility of condensation and mould growth. I have a cold flat roof ventilated by soffit vents on one side and no ventilation on the other side.

It is supplied with pre drilled fixing holes and an integral insect resistant grille. 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. Used to provide ventilation where flat roofs abut masonry. In this way the roof itself is kept cold.

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