Pitched Roof Air Gap

For more information on pitched roof insulation please see the kingspan kooltherm k7 pitched roof board brochure.

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. Kingspan with a warm roof the usual process is to split the insulation into two layers. For an unventilated roof without the use of counter battens a gap would need to be left for the breathable membrane to drape. 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 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. Ventilated roofs require a 50 mm air gap above the insulation timber stop battens can be nailed into the side of the rafters to give the correct air gap when. 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. At the ridge and also at the bottom either through vents at the eaves or.

It is important that air is allowed to circulate between the roof covering and the insulation to avoid condensation a gap of at least 50mm 2 inch must be left between the insulation and the inside of the roof covering. An unvented roof assembly is possible only if you keep the roof sheathing warm enough to prevent conditioned air from condensing against it.