Attic Insulation Vapor Barrier Or Not

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

Attic insulation vapor barrier or not.

Call attic insulation toronto for a free quote. When adding additional insulation to an attic that is already insulated never use insulation with a vapor barrier. 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. The insulation fiberglass or cellulose is then placed on top of the drywall with no vapor barrier above or below.

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. After the insulation is in place you will want to add a vapor retarder sometimes called a vapor barrier if you need one. Every construction material has an element of permeability to water which is why you need to have a vapor barrier to damp proof your home and 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.

Reasons for attic insulation 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. 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.

The heat being lost from the house below warmed up the attic so that moisture was lost through the vents as vapor. Not every wall does. 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.

A damp attic can also be the cause of discomfort and lower air quality in the living space. In any case the vapor barrier must point to the warm side.