9.25.5.1.General (See Note A-9.25.5.1.)

(1) Except as provided in Sentences (2) to (4), sheet and panel-type materials incorporated into assemblies described in Article 9.25.1.1. shall conform to Article 9.25.5.2. where (a) the material has (i) an air leakage characteristic less than 0.1 L/(s×m2) at 75 Pa, and (ii) a water vapour permeance less than 60 ng/(Pa×s×m 2) when measured in accordance with ASTM E96 / E96M, “Standard Test Methods for Water Vapor Transmission of Materials,” using the desiccant method (dry cup), and (See Note A-9.25.5.1.(1)(a)(ii)) (b) the intended use of the interior space where the materials are installed will not result in high moisture generation. (See Note A-9.25.5.1.(1)) (2) Where the intended use of the interior space will result in high moisture generation, the assembly shall be designed according to Part 5. (3) Wood-based sheathing materials not more than 12.5 mm thick and complying with Article 9.23.17.2. need not comply with Sentence (1). (See Note A-9.25.5.1.(3)) (4) Where a material has a water vapour permeance not less than 30 ng/(Pa×s×m2) and a thermal resistance not less than 0.7 (m2×K)/W and the heating degree-days of the building location are less than 6000, the assembly need not comply with Sentence (1).