Attic Insulation Vapor Barrier Or Not

Even if it asks you to.

Attic insulation vapor barrier or not.

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. Plastic vapor barriers should only be installed in vented attics in climates with more than 8 000 heating degree days. When considering the health of your attic the issue of moisture is exceedingly important. Attic insulation should always be installed with the paper backing facing toward the living space the ceiling in this case.

Adding a second vapor barrier could cause condensation to become trapped in the insulation between the two vapor barriers. 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. Not be trapped inside. After the insulation is in place you will want to add a vapor retarder sometimes called a vapor barrier if you need one.

Some regions don t require a vapor barrier. Vapor barriers in attics should only be installed on one side of the insulation. This acts as a barrier to keep heated moist air from rising up into the attic during cold weather. Fiberglass insulation must stay dry to be effective.

The heat being lost from the house below warmed up the attic so that moisture was lost through the vents as vapor. A damp attic can also be the cause of discomfort and lower air quality in the living space. 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. Vapor barriers are sheets of plastic or other material placed on one side of insulation sheets.

A vapor retarder is a material used to prevent water vapor from diffusing into the wall ceiling or floor during the cold winter. Never compress or fluff your insulation. 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. Not every wall does.