Do I Need A Vapor Barrier For Attic Insulation

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.

Do i need a vapor barrier for attic insulation. This worked well until we added large quantities of attic insulation. 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. The paper facing contains a layer of impermeable asphalt that prevents water vapor from passing through it. 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.

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. 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. I install my vapor barrier in the middle of the wall system between the two walls. In mixed climate areas the vapor barrier is optional depending on the total design of a building.

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. If you need a vapor barrier and your insulation is unfaced you must cover it with a polyethylene film. Such a location works both as a vapor barrier as well as an air barrier and eliminates the need for an external air barrier not a easy application on a multi storried building as well as any special electrical pans and their sealing. A vapor retarder is a material used to prevent water vapor from diffusing into the wall ceiling or floor during the cold winter.

Not every wall does. Hence the need to reduce moisture flow into the attic and the need for a vapor barrier. In cold climates a vapor barrier is almost always needed. The insulation fiberglass or cellulose is then placed on top of the drywall with no vapor barrier above or below.