Properties and position of materials and components installed to control air leakage and permit venting to the exterior as part of an air barrier system.

This applies to building materials, components, assemblies and their interfaces described in Sentence 5.1.2.1.(1) that are installed in buildings to which Part 5 applies [see Sentence 1.3.3.2.(1) of Division A for application of Part 5].

This also applies to the position of low air and vapour permeance materials within the building assembly relative to the position of materials providing thermal resistance in the assemblies of buildings to which Part 9 applies [see Sentence 1.3.3.3.(1) of Division A for application of Part 9], where the building assembly:

• incorporates low permeance materials that act as other than cladding or that are installed on the warm side of the assembly, and
• is more susceptible to condensation [see Sentences 9.25.1.2.(4) and (5) for combinations of interior and exterior environmental conditions that create a higher risk for condensation].

Exceptions: 

Where required life safety systems are incorporated in environmental separators, to limit the probability of the inadequate control of air leakage or inadequate venting, which could lead to the freezing of pipes, which could lead to compromised operation of temperature-sensitive or moisture-sensitive life safety systems, which could lead to harm to persons.