About Air Barriers

Materials, Components, Assemblies & Systems

The term air barrier needs to be better described. Many use the term when the actually mean a material, a component, an assembly or a system. These terms are defined as;

Air Barrier – Primary material that prevents or reduces the passage of air through the building enclosure system.

Air Barrier Material – principal element installed to provide a continuous barrier to the movement of air through building enclosures.

Air Barrier Components – transitional element installed to provide a continuous barrier to the movement of air through building enclosures.

Air Barrier Assembly - a collection of air barrier materials and air barrier components installed to provide a continuous barrier to the movement of air through building enclosures.

Air Barrier System – a combination of air barrier assemblies installed to provide a continuous barrier to the movement of air through building enclosures.

The air permeance of any air barrier material is 0.02L(s•m²) @ 75Pa. The air permeance of drywall is equal to this and is used as a control material. So any material that has a air permeance equal to or less that this value qualifies as a air barrier material. As you look at the materials used in a building you will find hundreds of materials that meet this requirement.

Having air barrier materials in a building does not provide you with a continuous plane of air tightness. To achieve this you must join the various air barrier materials together using air barrier components. These components connect one material to another material, a material to an assembly, and one assembly to another assembly. The air permeance of an air barrier component is 0.02L(s•m²) at 75 Pa.

An air barrier assembly is simply a collection of air barrier materials assembled together using air barrier components to provide a continuous plane of air tightness for that assembly (i.e. wall assembly). The maximum air leakage of an air barrier assembly should be 0.2 L(s•m²) @ 75 Pa.

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