Vapor Barrier Insulation Attic

When adding additional insulation to an attic that is already insulated never use insulation with a vapor barrier.

Vapor barrier insulation attic. 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. 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. In any case the vapor barrier must point to the warm side.

Some regions don t require a 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. Vapor barriers are sheets of plastic or other material placed on one side of insulation sheets. Vapor barriers keep the air moisture in your house from condensing in the insulated cavities.

The insulation fiberglass or cellulose is then placed on top of the drywall with no vapor barrier above or below. 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. 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 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 paper facing contains a layer of impermeable asphalt that prevents water vapor from passing through it. After the insulation is in place you will want to add a vapor retarder sometimes called a vapor barrier if you need one.