ABC gives three options for achieving an airtight building envelope: One prescriptive option (Clause (a)), and Two testing options (Clauses (b) and (c)).

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9.36.2.9. 1) The leakage of air into and out of conditioned spaces shall be controlled by constructing

a) a continuous air barrier system in accordance with Sentences (2) to (6), Subsection 9.25.3 and Article 9.36.2.10.,

b) a continuous air barrier system in accordance with Sentences (2) to (6) and Subsection 9.25.3. and a building assembly having an air leakage rate not greater than 0.20 L/(s*m²) (Type A4) when tested in accordance with CAN/ULC-S742, "Air Barrier Assemblies - Specification," at a pressure differential of 75 Pa, or

c) a continuous air barrier system in accordance with Sentences (2) to (6) and Subsection 9.25.3. and a building assembly having an air leakage rate not greater than 0.20 L/(s*m²) when tested in accordance with ASTM E 2357, "Determining Air Leakage of Air Barrier Assemblies."