Vapor Barrier For Attic Walls Thickness

I want to install insulation in my attic floor which i use for storage.

Vapor barrier for attic walls thickness.

Plastic specifically 6 mil polyethylene plastic is. 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. This wall assembly will dry from the vapor barrier inwards and will dry from the vapor barrier outwards. After the insulation is in place you will want to add a vapor retarder sometimes called a vapor barrier if you need one.

Whether or not you need a vapor retarder hinges on three main factors. Vapor barriers sheets of plastic or kraft paper keep water vapor out of the wall cavity so the insulation stays dry. A vapor retarder is a material used to prevent water vapor from diffusing into the wall ceiling or floor during the cold winter. My question is should iuse a vapor barrier inthe attic floor.

Vapor barriers are sheets of plastic or other material placed on one side of insulation sheets. In any case the vapor barrier must point to the warm side. Without a vapor barrier in place condensation inside the walls could ruin the insulation and promote the growth of harmful mold and bacteria. Not every type of insulation needs a vapor barrier.

On the other hand an air barrier a properly detailed air tight drywall ceiling for example in the absence of a vapor barrier can be effective since it stops the flow of vapor laden air. The previous owner has 1 foam insulation with a a plastic vapor barrier only on the rafters of the roof about4 from the slate roof but not on the walls of the attic. Even though we apply vapor barriers to exterior insulated walls in cold climates it s no longer recommended for ceilings floor of the attic. But if it does the barrier should face inside in northern heating climates and outside in humid southern climates.

Concrete block with interior frame wall cavity insulation and brick or stone veneer applicability limited to mixed humid hot humid mixed dry hot dry and marine regions should not be used in cold very cold and subarctic. A vapor barrier in an attic assembly in a severely cold climate with the absence of an air barrier will likely be ineffective. Because it s nearly impossible to seal penetrations in the ceiling the reality is water vapor will get into the attic. Not every wall does.

The science of moisture movement.