US Patent 8215339 Vapor barrier with valve for a building

A vapor barrier for sealing an interior of a building from an insulation cavity defined by framing members of the building includes a flexible and substantially impermeable sheet having apertures to allow air to exit the insulation cavity during filling of the insulation cavity with loose fill insulation. The vapor barrier also includes one-way valves mounted across the apertures. The valves are configured to allow air flow out of the insulation cavity and into the building interior through the apertures and to prevent air flow and moisture diffusion from the building interior into the insulation cavity.