Attic Insulation Vapor Barrier Or Not

Fiberglass insulation must stay dry to be effective.

Attic insulation vapor barrier or not.

A damp attic can also be the cause of discomfort and lower air quality in the living space. Not every wall does. Plastic vapor barriers should only be installed in vented attics in climates with more than 8 000 heating degree days. This acts as a barrier to keep heated moist air from rising up into the attic during cold weather.

When considering the health of your attic the issue of moisture is exceedingly important. This barrier is meant to keep moisture from getting to the insulation in the walls and ceilings and it is required by building codes when insulating most houses. Vapor barriers in attics should only be installed on one side of the insulation. Adding a second vapor barrier could cause condensation to become trapped in the insulation between the two vapor barriers.

Whether using loose fill or batts put the vapor barrier closest to the warm side of your installation where hot moist air would get in facing the house s interior in cold climates beneath floor insulation and the attic s interior in hot climates on top of floor insulation. A vapor retarder is a material used to prevent water vapor from diffusing into the wall ceiling or floor during the cold winter. Attic insulation should always be installed with the paper backing facing toward the living space the ceiling in this case. After the insulation is in place you will want to add a vapor retarder sometimes called a vapor barrier if you need one.

Vapor barriers are sheets of plastic or other material placed on one side of insulation sheets. You can forego the plastic and use a vapor retarder kraft faced insulation or latex ceiling paint in all other climates except hot humid or hot dry climates. Attic insulation vapor barrier or not. The heat being lost from the house below warmed up the attic so that moisture was lost through the vents as vapor.

Since some leakage of moisture into the insulation in inevitable murphy s law you want it to be able to freely escape from the insulation into the attic. You want to keep your attic as dry as possible to protect the area from mold and mildew as well as rot. Some regions don t require a vapor barrier. Before the introduction of attic insulation attics in cold climates were poorly insulated and plastic ceiling vapor barriers were omitted.