Weather Resistive Barriers

Weather resistive barriers are part of an exterior wall system designed to protect building materials from moisture penetration. There are different types of weather resistive barriers including vapor barriers, vapor retarders, air barriers and air retarders.

Not all air barriers are vapor barriers and not all vapor barriers are air barriers, however, all weather resistant barrier membranes must resist entry of liquid water (rain/snow) into the wall system by providing a drainage plane.

There are three general classes of membranes based on permeability.