For an air barrier system to be effective, all critical junctions and penetrations must be sealed using either an interior or exterior air barrier approach or a combination of both.

The following are examples of typical materials and techniques used to construct an interior air barrier system:

• Airtight-drywall approach
• Sealed polyethylene approach
• Joint sealant method
• Rigid panel material (ie. Extruded polystyrene)
• Spray-applied foams
• Paint or parging on concrete masonry walls or cast-in-place concrete

Where the air barrier and vapour barrier functions are provided by the same layer, it must be installed toward the warm (in winter) side of the assembly or, in the case of mass walls such as those made of cast-in place concrete, provide resistance to air leakage through much of the thickness of the assembly. Where these functions are provided by separate elements, the vapour barrier is required to be installed toward the interior of the assembly while the airtight element can be installed toward the interior or exterior depending on its vapour permeance.

The following are examples of typical materials and techniques used to construct an exterior air barrier system:

• Rigid panel material (i.e. Extruded polystyrene)
• House wraps
• Peel-and-stick membranes
• Liquid-applied membranes

• When designing an exterior air barrier system, consideration should be given to the strength of the vapour barrier and expected relative humidity levels as well as to the climatic conditions at the building's location and the properties of adjoining materials.