Does Attic Insulation Need 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.

Does attic insulation need vapor barrier.

This worked well until we added large quantities of attic insulation. Hence the need to reduce moisture flow into the attic and the need for a vapor barrier. Whether or not you need a vapor retarder hinges on three main factors. 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. In cold climates a vapor barrier is almost always needed. Not every wall does. The facing on faced insulation acts as a vapor retarder.

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. With the added insulation the attic stayed cold and so did the ventilating air from outside which was now unable to effectively remove attic moisture. A vapor retarder is a material used to prevent water vapor from diffusing into the wall ceiling or floor during the cold winter.

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.