Attic Insulation Vapor Barrier Direction

Not be trapped inside.

Attic insulation vapor barrier direction.

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. 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. The placement of the vapor barrier depends largely on the climate where your house is. 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. Joe says in the article plastic vapor barriers really are vapor barriers when things get wet. Adding a second vapor barrier could cause condensation to become trapped in the insulation between the two vapor barriers. 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 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. 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. In cold climates the opposite is true. A vapor retarder is a material used to prevent water vapor from diffusing into the wall ceiling or floor during the cold winter.

This acts as a barrier to keep heated moist air from rising up into the attic during cold weather. Not every wall does. 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. After the insulation is in place you will want to add a vapor retarder sometimes called a vapor barrier if you need one.

Also on the graph is the permeance of polyethylene. The wetter it gets the better it dries. Not so asphalt saturated kraft paper.