Attic Insulation Vapor Barrier Direction

Joe says in the article plastic vapor barriers really are vapor barriers when things get wet.

Attic insulation vapor barrier direction.

Attic insulation should always be installed with the paper backing facing toward the living space the ceiling in this case. The wetter it gets the better it dries. In cold climates the opposite is true. 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 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. Vapor barriers in attics should only be installed on one side of the insulation. If you put it on the right side where the humidity is it s not much of a vapor retarder. 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.

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

Never compress or fluff your insulation. The paper creates a vapor barrier that helps keep the water vapor in the warm moist heated indoor air from migrating outward into the wall or other structure. Not be trapped inside. This acts as a barrier to keep heated moist air from rising up into the attic during cold weather.

Also on the graph is the permeance of polyethylene. Adding a second vapor barrier could cause condensation to become trapped in the insulation between the two vapor barriers. Not so asphalt saturated kraft paper.