The Ontario Building Code | Vapour Barrier Materials

9.25.4.2. Vapour Barrier Materials

(1) Vapour barriers shall have a permeance not greater than 60 ng/(Pa∙s∙m²), measured in accordance with ASTM E96 / E96M, "water Vapor Transmission of Materials", using the desiccant method (dry cup).

(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) Where polyethylene is installed to serve as the vapour barrier, it shall conform to CAN/cgsb-51.34-M, "Vapour Barrier, Polyethylene Sheet for Use in building Construction".

(4) Membrane-typevapour barriers other than polyethylene shall conform to CAN/cgsb-51.33-M, "Vapour Barrier, Sheet, Excluding Polyethylene, for Use in Building Construction".

(5) Where a coating is applied to gypsum board to function as the vapour barrier, the permeance of the coating shall be determined in accordance with CAN/CGSB-1.501-M, "Method for Permeance of Coated Wallboard".

(6) Where insulation functions as the vapour barrier, it shall be sufficiently thick so as to meet the requirement of Sentence (1).