Air barriers control the unintended movement of air into and out of a building enclosure. Air barrier systems are made up of a number of materials that are assembled to provide a complete barrier to air leakage through the building enclosure.  A building enclosure includes all "six sides" of a building - exterior walls, roof, and foundation floor and may also include separations within the structure.

High performance buildings are designed with energy conserving features like air barrier systems to reduce air infiltration into the interior of the building. The addition of appropriate air barriers criteria contributes to enhanced sustainability by reducing heating and cooling loads. This results in less demand on the utility delivery systems in a community. This also requires less expenditure of materials and resources for construction of utility systems to meet increased utility demand to serve new buildings and using fewer natural resources to generate power thus helping to reduce the negative environmental impacts of non-renewable power generation.

High Performance Building Requriements for Sustainability-Summary of Significant Modifications to the 2009 International Building Code