Attic Insulation Vapor Barrier Or Not

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

Attic insulation vapor barrier or not.

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. Vapor barriers are sheets of plastic or other material placed on one side of insulation sheets. 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. 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. 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.

In any case the vapor barrier must point to the warm side. Reasons for attic insulation vapor barrier. 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. A vapor retarder is a material used to prevent water vapor from diffusing into the wall ceiling or floor during the cold winter.

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. 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. Some regions don t require a vapor barrier.

Call attic insulation toronto for a free quote. 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.