The Ontario Building Code | Installation of Vapour Barriers
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 barrierand the insulationhttp://thehandyforce.com/insulation/" title ="Toronto home insulation">insulation, the vapour barrier shall be installed sufficiently close to the warm side of the insulationhttp://thehandyforce.com/insulation/" title ="Toronto home insulation">insulation to prevent condensation at design conditions.
(3) Where the same product is used for the vapour barrier and the insulationhttp://thehandyforce.com/insulation/" title ="Toronto home insulation">insulation, the product shall be installed sufficiently close to the warm side of the assembly to prevent condensation at design conditions.
9.25.5. Properties and Position of Materials in building Envelope
In Plain Language
Vapour barriers must be installed as set out in this article, since gaps, tears, or poor sealing at seams can significantly undermine their effectiveness.
This is a plain-language summary of the 2012/2017 Ontario Building Code text above, for general understanding only and not a substitute for the Code. Always confirm current requirements against the 2024 edition (O.Reg. 163/24) or a qualified professional before construction.