Air barriers are permeable systems that allow vapor transmission through a wall assembly. Controlling air is crucial for the health and energy efficiency of buildings. Air barriers are essential elements of new building construction. Air naturally moves from warm to cold areas and moisture moves from humid to dry areas. In walls without air barriers, uncontrolled movement can result in condensation of moisture on cold surfaces. Uncontrolled flow of air and moisture can harm the long-term performance and durability of your building materials, decrease indoor air quality, lower energy efficiency and affect the health of your building and its occupants.