- 隔汽层 Vapor Retarder
- 气密性 Air Barrier
Roofing underlayment membranes made from materials such as polypropylene or polyethylene fabrics may be substituted for traditional building felt. These synthetic roofing underlayments tend to be lighter, more tearresistant, less sensitive to prolonged exposure to sunlight, and more costly than building felt.
Installing a polyethylene vapor retarder over glass fiber batt insulation using a staple hammer, which drives a staple each time it strikes a solid surface. The batts are unfaced and stay in place between the studs by friction.
Where vapor retarders are used, they are normally placed on the interior (warm) side of the insulation. Polyethylene plastic sheet, a Class I vapor retarder, is stapled to the face of wood framing after the insulation has been installed in the framing cavities.