Insulating Knee Walls Vapor Barrier

So before we get into the details there are a few choices to make.

Insulating knee walls vapor barrier.

Thus installing vapor barriers on wall surfaces must. 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. Wow there s a lot of new stuff there.

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. Whether your vapor barrier is a facing or a film it must be placed on the warm in winter side of the wall. Whether or not you need a vapor retarder hinges on three main factors. 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. In any case the vapor barrier must point to the warm side. The science of moisture movement. Not every wall does.

If you live in a hot humid climate. 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. The biggest heat loss problems with knee walls are those gigantic holes in the air barrier.

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.