Exterior Wall Construction Vapor Barrier

Vapor retarder use and placement.

Exterior wall construction vapor barrier.

Vapor barriers are sheets of plastic or other material placed on one side of insulation sheets. 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. Most authorities recommend vapor barriers in certain situations.

In any case the vapor barrier must point to the warm side. In certain climates vapor retarders can be a vital part of the wall construction. If dow and the other companies are correct in their information that a perm rating of about 10 is ideal for the exterior water vapor retarder for mixed humid climates then this would be a material that keeps out nearly 100 of wind driven rain water yet allows any. 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.

Determining the dewpoint for the interior environment locating the dewpoint in the wall construction. 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. This wall assembly will dry from the vapor barrier inwards and will dry from the vapor barrier outwards. The standard installation of a plastic vapor barrier is between the studs and the drywall but there are some exceptions to this.

Avoid adding interior vapor barriers where the outer wall construction already includes a material with vapor barrier properties. 1 the fundamentals of creating a proper vapor barrier include developing the thermal section of exterior wall or roof. Where is the wall located. In exterior walls that are below grade like basement walls.

In areas with high humidity such as greenhouses rooms with spas or swimming pools and bathrooms vapor barriers are often recommended. A vapor barrier reduces the movement of water vapor by. Let s consider the exterior water barrier vapor barrier retarder first.