Exterior Wall Vapor Barrier

Very hot and humid climates may benefit from an exterior vapor barrier that keeps outside humidity from penetrating into walls.

Exterior wall vapor barrier.

When a vapor barrier is on the side of a wall where the dry air is i e outside in winter or inside in summer moisture problems can occur. If a home already has a vapor retarder or vapor barrier it s important not to add another vapor impermeable layer on the opposite side of the wall that could trap moisture in the middle along. Such a wall system can be built with multiple thermal breaks with the weakest areas having an. The exterior face of the wall or floor cavity should remain permeable in order to allow dissipation of any moisture that does enter the wall cavity.

A vapor barrier s job is to keep water vapor in humid air from diffusing through one side of a wall and finding a cool surface inside the wall. In exterior walls that are below grade like basement walls. What s more on uninsulated houses that didn t have air conditioning a vapor barrier was not needed. Vapor barriers are sheets of plastic or other material placed on one side of insulation sheets.

The most important thing to remember when insulating exterior walls during renovations is to be sure not to trap moisture between two vapor barriers. This is then followed by a 2x4 wall with studs offset from exterior wall another 3 1 2 fiberglass or rockwool then sheetrock. 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. The standard installation of a plastic vapor barrier is between the studs and the drywall but there are some exceptions to this.

In any case the vapor barrier must point to the warm side. In hot climates any moisture that condenses on the exterior side of the vapor barrier will be drained to the exterior since the vapor barrier is also a drainage plane. The air circulation in the empty exterior wall cavity allowed any liquid water to evaporate and become a gas once again where it couldn t cause rot mildew or mold. Vapor retarder use and placement in certain climates vapor retarders can be a vital part of the wall construction.

Window door openings connect both walls with 1 2 underlayment plywood and are sealed to the vapor retarder air barrier. A vapor barrier reduces the movement of water vapor by.