Vapour Barrier Cold Flat Roof

A vapour control layer or vcl on a warm flat roof sits between the roof decking and the insulation.

Vapour barrier cold flat roof.

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. Room in the roof constructions often use a combination of warm and cold roof constructions with varying types of insulation. Including fibreglass roof kits torch on felt and liquid rubber products everything you need for flat roofing is in one place. Whether you re repairing a flat roof or laying a new one from scratch you ll find all the materials you need here.

Most diagrams on the internet i have seen have plasterboard on joist insulation air gap osb board then roofing material. Cold roof areas usually include vapour open fibrous insulation e g mineral wool quilt. Bituminous vapour retarders asphalt mixed with felt or fiberglass or non bituminous vapour retarders plastic. Frame wall with cavity insulation and brick or stone veneer with interior vapor barrier.

Including flat roof vapour barrier for extra secure roofing solutions. I am building a cold flat roof on an extension. I have recently finished installing a celotex warm roof to my house i have several sheets left over my flat roof extension needs to be recovered and insulated also as a warm roof can i use the 100 mm ga 4000 insulation boards i have left over for this project if so would i need to use a vapour control barrier or would taping the joints act. 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.

Do i need a vapour barrier between the plasterboard and the bottom of the joist. The notion behind a vapour control layer is to install it on the room. Applicability limited to very cold subarctic and arctic regions. This wall is a further variation of figure 6 but now it has a class i vapor retarder on the interior a vapor barrier completely eliminating any inward drying potential.

When the temperature of the vapour falls to or below its dew point the water vapour condenses on cold surfaces.