Does Attic Insulation Need 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.

Does attic insulation need vapor barrier.

If you are planning to have an attic insulation project for your home you may be wondering whether it is important to have a vapor barrier installed as well. 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. The paper facing contains a layer of impermeable asphalt that prevents water vapor from passing through it. The insulation fiberglass or cellulose is then placed on top of the drywall with no vapor barrier above or below.

Not every wall does. 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. In mixed climate areas the vapor barrier is optional depending on the total design of a building. After the insulation is in place you will want to add a vapor retarder sometimes called a vapor barrier if you need one.

The facing on faced insulation acts as a vapor retarder. This worked well until we added large quantities of attic insulation. If you need a vapor barrier and your insulation is unfaced you must cover it with a polyethylene film. Hence the need to reduce moisture flow into the attic and the need for a vapor barrier.

To be able to answer this question correctly for your home there are a few factors you need to consider before any major attic insulation project.