Do I Need A Vapor Barrier For Attic Insulation

The paper facing contains a layer of impermeable asphalt that prevents water vapor from passing through it.

Do i need a vapor barrier for 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. 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. I install my vapor barrier in the middle of the wall system between the two walls. This worked well until we added large quantities of attic insulation.

Not every wall does. Whether or not you need a vapor retarder hinges on three main factors. In mixed climate areas the vapor barrier is optional depending on the total design of a building. 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.

Hence the need to reduce moisture flow into the attic and the need for a 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. The insulation fiberglass or cellulose is then placed on top of the drywall with no vapor barrier above or below. After the insulation is in place you will want to add a vapor retarder sometimes called a vapor barrier if you need one.

Do not overlook attic access door. In cold climates a vapor barrier is almost always needed. 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. To install an efficient vapor barrier you need the dimensions of the room.

The facing on faced insulation acts as a vapor retarder. If you need a vapor barrier and your insulation is unfaced you must cover it with a polyethylene film. 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. Take the measurements with you when purchasing materials.

A vapor retarder is a material used to prevent water vapor from diffusing into the wall ceiling or floor during the cold winter.