Does Attic Insulation Need Vapor Barrier

The insulation fiberglass or cellulose is then placed on top of the drywall with no vapor barrier above or below.

Does attic insulation need vapor barrier.

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. Hence the need to reduce moisture flow into the attic and the need for 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.

In mixed climate areas the vapor barrier is optional depending on the total design of a building. If you need a vapor barrier and your insulation is unfaced you must cover it with a polyethylene film. 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. Whether or not you need a vapor retarder hinges on three main factors.

The paper facing contains a layer of impermeable asphalt that prevents water vapor from passing through it. 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. In cold climates a vapor barrier is almost always needed. Not every wall does.

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.