Code Library › Volume 1 › Section 9.25 — Heat Transfer, Air Leakage and
PART 9 — HOUSING AND SMALL BUILDINGSUpdated for the 2024 Ontario Building Code

9.25.4.3.Installation of Vapour Barriers

(1) Products installed to function as the vapour barrier shall protect the warm side of wall, ceiling and floor assemblies. (2) Where different products are used for the vapour barrier and the insulation, the vapour barrier shall be installed sufficiently close to the warm side of the insulation to prevent condensation at design conditions. (See Notes A- 9.25.4.3.(2) and A-9.25.5.1.(1)) (3) Where the same product is used for the vapour barrier and the insulation, the product shall be installed sufficiently close to the warm side of the assembly to prevent condensation at design conditions. (See Notes A-9.25.4.3.(2), A- 9.25.5.1.(1) and A-9.25.5.2.)
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Code text is reproduced for reference from the Ontario Building Code (O. Reg. 163/24, 2024 Building Code Compendium). This page is provided for general information and is not an official copy. Always verify requirements against the official Ontario Building Code and confirm with your local building department.