Terms of the Trade: What Is a Vapor Barrier?
Vapor barriers limit the movement of warm, most air into the wall cavity. If the air were to move there, it can lessen the effectiveness of insulation and even promote the growth of mold. The most common type of vapor barrier material is plastic sheeting covering fiberglass batting, but kraft-faced paper is also used when stapled into individual stud cavities. However, this variety isn't as seamless as plastic sheeting and must be covered for fire prevention purposes.