Exterior Wall Vapor Barrier

What s more on uninsulated houses that didn t have air conditioning a vapor barrier was not needed.

Exterior wall vapor barrier.

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. Vapor retarder use and placement in certain climates vapor retarders can be a vital part of the wall construction. 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. 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.

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. If you are adding an exterior wall anywhere in the house and you answered yes to either of the above questions you should consider using a vapor retarder. This wall assembly will dry from the vapor barrier inwards and will dry from the vapor barrier outwards. Very hot and humid climates may benefit from an exterior vapor barrier that keeps outside humidity from penetrating into walls.

A vapor barrier reduces the movement of water vapor by. 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. In any case the vapor barrier must point to the warm side. This is then followed by a 2x4 wall with studs offset from exterior wall another 3 1 2 fiberglass or rockwool then sheetrock.

Window door openings connect both walls with 1 2 underlayment plywood and are sealed to the vapor retarder air barrier. Such a wall system can be built with multiple thermal breaks with the weakest areas having an. In exterior walls that are below grade like basement walls. 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. The standard installation of a plastic vapor barrier is between the studs and the drywall but there are some exceptions to this.