Attic Insulation Vapor Barrier

The paper facing contains a layer of impermeable asphalt that prevents water vapor from passing through it.

Attic insulation vapor barrier.

A vapor retarder is a material used to prevent water vapor from diffusing into the wall ceiling or floor during the cold winter. Now with attic insulation heat is no longer lost from the living space such that moisture may remain trapped in the attic vapor barriers were therefore necessary to reduce moisture flow into the attic. Not every wall does. Vapor barriers are sheets of plastic or other material placed on one side of insulation sheets.

When adding additional insulation to an attic that is already insulated never use insulation with a vapor barrier. 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. If you live in a cold climate place the vapor barrier between the interior of your home and the insulation. Most forms of attic insulation benefit from the addition of a vapor barrier to protect them from the harmful effects of moisture which can reduce their effectiveness over time the following are a few simple steps to help you undertake the task properly so your vapor barrier retains heat without damaging the insulation.

If you do there is a chance that moisture that has slipped by the first vapor barrier will become trapped by the second vapor barrier decreasing the value of your insulation. The heat being lost from the house below warmed up the attic so that moisture was lost through the vents as vapor. The insulation fiberglass or cellulose is then placed on top of the drywall with no vapor barrier above or below. Vapor barriers keep the air moisture in your house from condensing in the insulated cavities.

Whether your vapor barrier is a facing or a film it must be placed on the warm in winter side of the wall. Do not add a vapor barrier on top of the insulation in your attic since the paper facing on the existing insulation is the vapor barrier. Attic vapor barrier detail for cold climates 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. In any case the vapor barrier must point to the warm side.