AbstractAir-barrier systems (ABSs) are essential elements in the performance of building envelopes and they are specified in the National Building Code of Canada (NBC) to minimize the infiltration and exfiltration of air through the building envelope to control the risk of condensation. Although their primary function is to control the movement of air across the building envelope, when placed on the exterior side of the wall assembly, the barrier may also function as a water-resistive membrane, thereby reducing the movement of moisture toward the inside of the assembly. Since the publication of the Energy Code of Canada in 2014, more attention has been paid to the importance of ABS to control both heat flow and air transfer through the building envelope, which both contribute to rising costs of energy use in buildings. Recently, the Canadian Construction Materials Centre (CCMC) developed performance criteria for liquid-applied ABS. The CCMC is a recognized accreditation body that provides guidance to building officials with respect to the conformity of innovative products as alternative solutions to the NBC. In this paper, four key items are presented. First, a brief overview of liquid-applied ABS, their components and functions, and the motivation to use this product type in the construction industry is provided. Second, the qualification process for such product against requirements for compliance with the NBC in Canada and its market acceptance will be discussed. In doing so, the strategy recently adopted by the CCMC in the evaluation of innovative liquid-applied ABS will be reviewed. Third, the key performance criteria and the durability assessment for an expected 25 years of acceptable service life will be discussed. Finally, the quality control process for acceptable field applications will be briefly surveyed.

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