Pitched Roof Air Gap

If you are constructing a ventilated roof insulating between and under the rafters then there needs to be a 50 mm air gap between the insulation and the sarking felt to avoid condensation building up.

Pitched roof air gap. At the ridge and also at the bottom either through vents at the eaves or. There will also be kooltherm k7 pitched roof board between the rafters image credit. Kingspan with a warm roof the usual process is to split the insulation into two layers. The map at right which is based on table r806 4 of the irc lists the minimum r values required to prevent condensation in unvented assemblies in various climate zones.

This gap must be ventilated at the top i e. If 180mm is to be installed then 100mm board might be introduced between the rafters there has to be a minimum 25mm air gap between the insulation and the underside of. An air gap in the rafters is not required as long as there is a channel for water drainage to run down the roof this can be achieved with counter battens that run vertically down the roof. For more information on pitched roof insulation please see the kingspan kooltherm k7 pitched roof board brochure.

Find out about insulating a pitched roof at rafter level and the number of key design considerations which will affect the build up of the roof and the choice of insulation. An unvented roof assembly is possible only if you keep the roof sheathing warm enough to prevent conditioned air from condensing against it.