Ottawa By-law 2013-416, s. 67 — Property Standards By-law

1) Every basement, cellar or unheated crawl space shall be adequately vented to the outside air by means of screened windows which can be opened or by louvres with screened openings, the area of which shall not be less than one per cent (1%) of the 2 2 floor area for basements and 0.09 m (1 sq. ft.) for every 46.5 m (500 sq. ft.) of crawl space area. 2) Despite subsection (1), an opening for natural ventilation is not required if mechanical ventilation is provided which changes the air once each hour. PART IV VACANT BUILDINGS AND VACANT LANDS