The Ontario Building Code | Ventilation of Unheated Crawl Spaces
9.18.3.1. ventilation of Unheated Crawl Spaces
(1) Unheated crawl spaces shall be ventilated by natural or mechanical means.
(2) Where an unheated crawl space is ventilated by natural means, ventilation shall be provided to the outside air by not less than 0.1 m² of unobstructed vent area for every 50 m² of floor area.
(3) vents shall be,
(a) uniformly distributed on opposite sides of the building, and
(b) designed to prevent the entry of snow, rain and insects.
In Plain Language
Unheated crawl spaces need ventilation meeting the requirements set out in this article, managing moisture buildup in this unconditioned space.
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.