Vapour Barrier Flat Warm Roof

Flat roof vapour barrier materials when constructing a flat roof there are two types of materials commonly used.

Vapour barrier flat warm roof.

The roof is an unventilated warm roof design finished with a single ply membrane. Condensation is generated when warm moist air rises and condenses into a liquid on contact with the cooler areas above the insulation. It appears now when vapor retarders are needed more than ever the design community seems to have lost interest which is not good considering how codes and standards altered through concerns for energy savings have changed how buildings are designed constructed and operated. The architect plans stated requirement for a vapour control layer below the insulation or a 3 in 1 insulation board including vapour control layer and an additional foil backed plasterboard.

It has transpired that there is no vapour control layer fitted. Often the vcl in a warm roof is bonded to a timber substrate which helps the integrity however in a warm roof the vcl has two important functions. I m in the process of building a warm flat roof for a garden room and need to put down a vapour barrier between the sub deck and insulation. Bituminous vapour retarders asphalt mixed with felt or fiberglass or non bituminous vapour retarders plastic.

A flat roof vapour barrier such as iko s mvp modified vapour protector offers appropriate moisture protection. The need for use and design of a vapor retarder in the design of a roof system used to be a hotly debated topic. I was looking to use this vapour barrier from screwfix but not sure if it s suitable for the job it only mentions underfloor heating and laminate flooring in the description. Discussion in roofing and guttering started by sam85 21 jul 2017.

Much like the cold roof it stops the transfer of warm moist air from inside the building into the warm roof layers. I am having an extension built and my builder is constructing the flat warm deck roof in the following way. The vcl is easier to maintain in a warm roof construction as it s generally out the way of the dangers of plasterboard fixings and downlighters. The notion behind a vapour control layer is to install it on the room side of the insulation so it stops the passage of warm moist air entering the structure.

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