Insulating Knee Walls Vapor Barrier

Whether or not you need a vapor retarder hinges on three main factors.

Insulating knee walls vapor barrier.

The number one most important step in insulating and air sealing a knee wall is having a continuous air barrier. A vapor retarder is a material used to prevent water vapor from diffusing into the wall ceiling or floor during the cold winter. Insulation air sealing. This barrier is meant to keep moisture from getting to the insulation in the walls and ceilings and it is required by building codes when insulating most houses.

Vapor barriers are sheets of plastic or other material placed on one side of insulation sheets. After the insulation is in place you will want to add a vapor retarder sometimes called a vapor barrier if you need one. The science of moisture movement. If you live in a cold climate place the vapor barrier between the interior of your home and the insulation.

Knee walls have r 13 fiberglass rolls also called batts in them covered with stapled on reflective insulation. So before we get into the details there are a few choices to make. I ll deal with double vapor barriers more fully in another post let s take a look at a diagram of a finished knee wall job from energy smart home performance. Vapor barriers keep the air moisture in your house from condensing in the insulated cavities.

Water vapor can pass through building materials in several ways including direct transmission and by heat transfer but studies suggest that fully 98 percent of the moisture transfer through walls occurs through air gaps including cracks around electrical fixtures and outlets and gaps along baseboards. Not every wall does. In any case the vapor barrier must point to the warm side. If you live in a hot humid climate.

The biggest heat loss problems with knee walls are those gigantic holes in the air barrier.