Vapor Membrane Roof

Typically a vapor retarder has to have a perm rating of 1 0 or less to be successful.

Vapor membrane roof.

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. That reduction of air and moisture infiltration can then help improve roof longevity. A vapor retarder is a material or system that is designed as part of the roof system to substantially reduce the movement of water vapor into the roof system where it can condense. A separate air barrier would need to be installed below the membrane likely below the insulation layer as well.

In fact it is almost a perfect vapor barrier. Vapor control membranes play a very important role in this. The purpose of a vapor retarder is to minimize or reduce water vapor diffusion into a low slope roof or wall system. The firestone v gard vapor control membrane is designed to be used as vapor control layer in firestone roofing systems.

The roof is a large part of the building envelope and therefore has a significant impact on the flow of energy in and out of buildings. Everyone knows that water in roof systems is never a positive. When discussing air barriers roofing membranes and the building envelope another important topic comes to mind. The bottom membrane s primary function is that of an air barrier but it s material characteristics are such that historically it has also been a vapor barrier.

The billowing roof membrane can also create a sound issue for the owner as it flaps up and down. And the membrane on the bottom is also a vapor barrier.