Section 5.4 — Air Leakage

(1) Where a building component or assembly separates interior conditioned space from exterior space, interior space from the ground, or environmentally dissimilar interior spaces, the properties and position of the materials and components in those components or assemblies shall be such that they control air leakage or permit venting to the exterior so as to (a) provide acceptable conditions for the building occupants, (b) maintain appropriate conditions for the intended use of the building, (c) minimize the accumulation of condensation in and the penetration of precipitation into the building component or assembly, (d) control heat transfer to roofs where ice damming can occur, (e) minimize the ingress of airborne radon and other soil gases from the ground with an aim to controlling the indoor concentrations of these gases to an acceptable level, and (f) not compromise the operation of building services. (2) Except as provided in Sentence (7), an air barrier system shall be designed and constructed to provide the principal resistance to air leakage to meet the requirements of Sentence (1). (3) The air barrier system shall incorporate air barrier assemblies that meet the appropriate Performance Class as defined in Table 5.4.1.1. (See Note A-5.4.1.1.(3)) Table 5.4.1.1. Maximum Air Leakage Rates for Air Barrier Assemblies Forming Part of Sentences 5.4.1.1.(3) and (6) and 5.4.1.2.(1) and (2) Performance Class Maximum Air Leakage Rate, L / (s × m2), at a Pressure Differential of 75 Pa 1 0.05 2 0.10 3 0.15 4 0.20 5 0.50 (4) The air barrier system shall be designed and constructed to be continuous (a) across construction, control and expansion joints, (b) across junctions between different air barrier assemblies, and (c) around penetrations through air barrier assemblies. (See Note A-5.4.1.1.(4)) (5) The structural design of air barrier assemblies, including junctions between air barrier assemblies, subject to air pressure loads shall comply with Article 5.1.4.1. and Subsection 5.2.2. (6) The maximum air leakage rates specified in Table 5.4.1.1. are permitted to be increased where it can be shown that the higher rate will not adversely affect any of (a) the health or safety of the building users, (b) the intended use of the building, or (c) the operation of building services. (7) An air barrier system is not required where it can be shown that uncontrolled air leakage will not adversely affect any of (a) the health or safety of building users, (b) the intended use of the building, or (c) the operation of building services. (See Note A-5.4.1.1.(7))

(1) Except as provided in Sentences (2) and (3), air barrier assemblies not in contact with the ground shall (a) conform with CAN/ULC-S742, “Standard for Air Barrier Assemblies – Specification,” and (b) meet the selected Performance Class of Table 5.4.1.1. (See Note A-5.4.1.2.(1)) (2) Air barrier assemblies not evaluated in accordance with CAN/ULC-S742, “Standard for Air Barrier Assemblies – Specification,” shall be designed and constructed (a) to meet or exceed the selected Performance Class of Table 5.4.1.1., and (b) with at least one air barrier material intended to provide the primary resistance to air leakage that meets the requirements of CAN/ULC-S741, “Standard for Air Barrier Materials – Specification.” (See Note A-5.4.1.2.(2)) (3) Air barrier assemblies covered in Subsections 5.9.2., 5.9.3. and 5.9.4. shall meet the air barrier performance criteria defined in those Subsections. (4) Below-grade air barrier assemblies in contact with the ground shall minimize the ingress of airborne radon and other soil gases. (See Note A-5.4.1.2.(4))