Attic Insulation Vapor Barriers

Identification

• Vapor barriers are more accurately described using the term "vapor diffusion retarders," because they do not provide a complete moisture barrier but rather slow down the rate at which moisture is absorbed through materials. Vapor barriers are used to retard moisture in ceilings, walls, basements and crawl spaces. Materials used as vapor barriers are measured in units of permeability, often referred to as "perms." The United States Department of Energy considers any material with a perm rating of 1.0 or less a vapor barrier.

Types

• Many types of attic insulation have vapor barriers. These barriers are usually tarpaper or plastic sheets. Blanket insulation comes in batts or rolls and often has a facing attached that acts as a vapor barrier; it is usually made from vinyl, plastic or kraft paper. If your existing attic insulation does not have a vapor barrier attached, painting your attic ceiling will provide a vapor barrier. Applying multiple coats of paint to the interior ceiling of your attic will slow moisture and reduce damage.

Benefits

• Installing attic insulation with a vapor barrier will reduce heat loss through the ceiling in your attic and reduce the amount of moisture that seeps into your attic space. When large amounts of excess moisture infiltrate your attic, it makes insulation less effective and may lead to mold growth. Once mold begins to grow, it eventually cause structural damage to your home and may cause health problems for you and your family. Inhaling mold spores can cause serious allergic reactions in sensitive people.

Considerations

• You can do other things to ensure your home is as energy efficient as possible. Check your attic hatch for weatherstripping and be sure it closes tightly. Inspect areas around duct work, pipes and chimneys for gaps and air leaks. Seal any gaps with caulk or a permanent sealant. Make sure your attic vents are not blocked by insulation and place insulation on your attic floor as well as the ceiling.