Vapor Barrier Roof Insulation

That reduction of air and moisture infiltration can then help improve roof longevity.

Vapor barrier roof insulation.

A vapour barrier sometimes referred to as vapour retarder is typically a plastic or foil sheet used for damp proofing to prevent interstitial condensation from forming in various building assemblies such as walls roofs foundations and floors. What is a vapour barrier. An introduction to vapour barriers and vapour retarders. Vapor barriers usually composed of a thin film such as polyethylene vapor barriers are used to retard or prevent water vapor diffusion into a wall ceiling or floor during the cold winter.

Not every wall does. Avoidance of the installation of vapor barriers such as polyethylene vapor barriers foil faced batt insulation and reflective radiant barrier foil insulation on the interior of air conditioned assemblies a practice that has been linked with moldy buildings lstiburek 2002. In any case the vapor barrier must point to the warm side. A vapor retarder is a material used to prevent water vapor from diffusing into the wall ceiling or floor during the cold winter.

A roof design that includes an adhered roof membrane with multiple layers of insulation with board joints offset and staggered over a vapor retarder air barrier helps lower the risk that air and the moisture it carries will infiltrate the roof system. After the insulation is in place you will want to add a vapor retarder sometimes called a vapor barrier if you need one.