Cold Flat Roof Construction Ventilation

Their layer of insulation is beneath the roof decking and the roofing membranes.

Cold flat roof construction ventilation.

I have an outbuilding which has a cold flat roof construction. However where vapour permeable or low resistance lr underlays are specified the levels required may be reduced. Cold roof voids are generally always required to be ventilated. That means the rest of the roof is protected from heat.

This significantly reduces the amount of rising heat and in turn condensation. However there is currently no ventilation and i am concerned that during the colder months warm air from the room below will rise up and meet with the colder air forming condensation and water droplets. 2011 code of practice for control of condensation in buildings stipulates that there should be a ventilation gap between the insulation and the bottom of the flat roof deck of at least 50mm. The enclosed void of a warm pitched roof may not require to be ventilated but this is usually subject to the requirement to install a fully sealed air and vapour control layer avcl in conjunction with an air open roof covering.

In a concrete deck for example this gap could be created by fixing 50x50mm timber battens at 600mm centres and attaching the insulation to underside of these battens. A ventilation gap usually 50mm should be. Ventilation for cold roofs. Cold deck flat roof the thickness of insulation required will vary depending on the material you decide to use and the manufacturer s specification.

The flat roof is finished in grp. A cold roof really is colder than the rest of your home in the winter which means condensation is much less likely to develop. In many cases cold roofs are used in storage spaces where there is no habitation occurring underneath. Hopefully this video will help explain the difference between cold flat roof construction and warm flat roof construction this videos show detailed drawings.