Insulation Vapour Barrier Attic

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

Insulation vapour barrier attic.

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. 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. Some regions don t require a 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.

The insulation fiberglass or cellulose is then placed on top of the drywall with no vapor barrier above or below. The paper facing contains a layer of impermeable asphalt that prevents water vapor from passing through it. 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. A vapor barrier in an attic assembly in a severely cold climate with the absence of an air barrier will likely be ineffective.

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

If you live in a cold climate place the vapor barrier between the interior of your home and the insulation. Not every wall does. After the insulation is in place you will want to add a vapor retarder sometimes called a vapor barrier if you need one. Vapor barriers are sheets of plastic or other material placed on one side of insulation sheets.