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Systems theory on biological and social systems

The air barrier system also separates garages from conditioned spaces. In this regard the air barrier system is also the “gas barrier” and provides the gas-tight separation between a garage and the remainder of the house or building.

Typical configurations of air barrier system enclosures are illustrated in Figure 1.



Air barriers are intended to resist the air pressure differences that act on them. Rigid materials such as gypsum board, exterior sheathing materials like plywood or OSB, and supported flexible barriers are typically effective air barrier systems if joints and seams are sealed. Spray foam systems can also act as effective air barrier systems either externally applied over structural elements or internally applied within cavity systems.

Air barrier systems keep outside air out of the building enclosure or inside air out of the building enclosure depending on climate or configuration. Sometimes, air barrier systems do both.

Air barrier systems can be located anywhere in the building enclosure – at the exterior surface, the interior surface, or at any location in between. In cold climates, interior air barrier systems control the exfiltration of interior, often moisture-laden air. Whereas exterior air barrier systems control the infiltration of exterior air and prevent wind-washing through cavity insulation systems.

Air barrier systems should be:

  • impermeable to air flow;
  • continuous over the entire building enclosure or continuous over the enclosure of any given unit;
  • able to withstand the forces that may act on them during and after construction;
  • durable over the expected lifetime of the building.