Exterior Wall Vapor Barriers

In exterior walls that are below grade like basement walls.

Exterior wall vapor barriers. 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. All have been evaluated by the air barrier association of america abaa and meet the most stringent energy codes including. A vapor barrier reduces the movement of water vapor by. Vapor barriers are sheets of plastic or other material placed on one side of insulation sheets.

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. Where is the wall located. Vapor barriers are used to stop water vapor a gas from entering a wall cavity where it can turn into liquid water if the water vapor contacts a cool or cold surface. The standard installation of a plastic vapor barrier is between the studs and the drywall but there are some exceptions to this.

And the canadian national. Ccw provides three types of air barriers. 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. If this happens and the water can t evaporate rapidly back into a gas wood rot mold and mildew become a reality.

A vapor barrier against the concrete surface is generally recommended before wood framing or flooring materials are installed. The few holes in this barrier required for exterior lights switches can be easily sealed with a can of foam or silicone mushroomed on both sides of the vapor barrier. Massachusetts energy code 780 cmr. 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.

Vapor retarder use and placement. 2010 2013 ashrae 90 1. In any case the vapor barrier must point to the warm side. 2012 2015 iecc.

This wall assembly will dry from the vapor barrier inwards and will dry from the vapor barrier outwards. To thwart the comments of the expense of the double wall headed my way i would like to add that the second wall that i add to the interior is totally non structural 24 o c. In certain climates vapor retarders can be a vital part of the wall construction. Dupont tyvek drainwrap is a moisture barrier designed to provide enhanced drainage in areas subject to extreme wind driven rain.

It combines the superior air and water resistance vapor permeability and strength of tyvek with a vertically grooved surface to help channel water safely to the outside.