Attic Insulation Vapor Barrier Direction

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

Attic insulation vapor barrier direction. In warm climates the barrier should point to the outside of the house blocking the vapor from the humid outside air that may seep into the walls or ceilings. Never compress or fluff your insulation. If the insulation is installed with the paper vapor barrier facing away from the heated part of the home moisture from humid inside air can condense and become trapped in the insulation during cold winter months. The wetter it gets the better it dries.

In cold climates the opposite is true. Vapor barriers in attics should only be installed on one side of the insulation. Not be trapped inside. Joe says in the article plastic vapor barriers really are vapor barriers when things get wet.

Attic insulation should always be installed with the paper backing facing toward the living space the ceiling in this case. If you put it on the right side where the humidity is it s not much of a vapor retarder. After the insulation is in place you will want to add a vapor retarder sometimes called a vapor barrier if you need one. Adding a second vapor barrier could cause condensation to become trapped in the insulation between the two vapor barriers.

The purpose of insulation facing the facing on kraft faced insulation is made of kraft paper with an asphalt coating that makes the paper impermeable to water vapor. Not every wall does. The insulation fiberglass or cellulose is then placed on top of the drywall with no vapor barrier above or below. Since some leakage of moisture into the insulation in inevitable murphy s law you want it to be able to freely escape from the insulation into the attic.

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. Also on the graph is the permeance of polyethylene. The placement of the vapor barrier depends largely on the climate where your house is.