Insulation Vapour Barrier Attic

After the insulation is in place you will want to add a vapor retarder sometimes called a vapor barrier if you need one.

Insulation vapour barrier attic.

A vapor retarder is a material used to prevent water vapor from diffusing into the wall ceiling or floor during the cold winter. Vapor barriers keep the air moisture in your house from condensing in the insulated cavities. 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. 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. The paper facing contains a layer of impermeable asphalt that prevents water vapor from passing through it. Whether your vapor barrier is a facing or a film it must be placed on the warm in winter side of the wall.

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. 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. The insulation fiberglass or cellulose is then placed on top of the drywall with no vapor barrier above or below.

On the other hand an air barrier a properly detailed air tight drywall ceiling for example in the absence of a vapor barrier can be effective since it stops the flow of vapor laden air. Some regions don t require a vapor barrier. A vapor barrier in an attic assembly in a severely cold climate with the absence of an air barrier will likely be ineffective. 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.