Install Attic Insulation Vapor Barrier

The science of moisture movement.

Install attic insulation vapor barrier.

Vapor barriers are sheets of plastic or other material placed on one side of insulation sheets. Thus installing vapor barriers on wall surfaces must. If there is limited lighting find a way to provide more so you can see what you re doing. Not be trapped inside.

Begin the process of fitting a vapor barrier for attic insulation by preparing the space for the job. A plastic vapor barrier is best installed in a vented attic within climates with over 8 000 heating degree days. Never compress or fluff your insulation. In any case the vapor barrier must point to the warm side.

Remove any transferable items from the attic so that they do not get in the way as you work. Adding a second vapor barrier could cause condensation to become trapped in the insulation between the two vapor barriers. Some regions don t require a vapor barrier. The paper creates a vapor barrier that helps keep the water vapor in the warm moist heated indoor air from migrating outward into the wall or other structure.

Water vapor can pass through building materials in several ways including direct transmission and by heat transfer but studies suggest that fully 98 percent of the moisture transfer through walls occurs through air gaps including cracks around electrical fixtures and outlets and gaps along baseboards. 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. This acts as a barrier to keep heated moist air from rising up into the attic during cold weather. The best approach for a vented attic in a cold climate is installing a layer of drywall with a good coat of latex paint the paint creates a semi permeable vapor barrier.

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. Attic insulation should always be installed with the paper backing facing toward the living space the ceiling in this case. 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. The insulation fiberglass or cellulose is then placed on top of the drywall with no vapor barrier above or below.