Vapour Barrier For Cold Flat Roof

Do i need a vapour barrier between the plasterboard and the bottom of the joist.

Vapour barrier for cold flat roof.

Room in the roof constructions often use a combination of warm and cold roof constructions with varying types of insulation. It s the first line of defence against high vapour pressure air entering the roof structure and causing interstitial condensation. Bituminous vapour retarders asphalt mixed with felt or fiberglass or non bituminous vapour retarders plastic. Most diagrams on the internet i have seen have plasterboard on joist insulation air gap osb board then roofing material.

The sloping ceiling areas include closed cell or foil backed rigid board insulants most of which are highly vapour resistant. Why is it the best vapour barrier for flat roofs. Flat roof vapour barrier materials when constructing a flat roof there are two types of materials commonly used. Cold roof areas usually include vapour open fibrous insulation e g mineral wool quilt.

Condensation within a flat roof mainly occurs during cold weather when moisture vapour in the air which has been generated within the heated building rises from the room below into the cold roof void above the ceiling. A flat roof vapour barrier such as iko s mvp modified vapour protector offers appropriate moisture protection. Temporarily waterproofs the roof can stay uncovered for up to 3 months. When the temperature of the vapour falls to or below its dew point the water vapour condenses on cold surfaces.

Which ventilation solutions are available. For cold flat roofs the vapour layer needs to be positioned underneath the insulation layer on top of the room below to create an effective barrier. Its not cheap purchasing it by the role and by the pallet load is cheaper but is a considerable layout. Vapour resistance of 2000 mns g.

I am building a cold flat roof on an extension. In general the installation of a cold roof is not recommended for the construction of new properties. A vapour control layer helps you shield your building from the consequences of condensation condensation is generated when warm moist air rises and condenses into a liquid on contact with the cooler areas above the insulation. Self healing if punctured by fixings.

Because of this the vcl always sits at the warm side of the. The notion behind a vapour control layer is to install it on the room.