I have been receiving many questions and concerns regarding Radon gas in relation to both existing dwellings and new development. I reached out to City staff to gather the most accurate information regarding the City’s approach/advice on this and this is what they said:
All new buildings containing normally occupied areas in contact with the ground (houses, multiplexes, apartment buildings, etc.) shall be designed to account for the potential presence of radon, and shall be designed such that a radon extraction system may be installed in such cases when 3-month testing reveals high levels of radon are present.
Building Code Services has produced bilingual advisories speaking to the current Ontario Building Code (OBC) requirements, and Ottawa Public Health and Health Canada have produced information on this topic, all found on Ottawa Public Health’s Radon in Your Home website. The OBC treats new low-rise housing & small buildings differently from new large & complex buildings; however, radon must nonetheless be accounted for in both instances.
Because high radon concentrations are found sporadically in any given geographical area of the city or province (one street may have a handful of homes with high radon levels and many others on the same street may have low levels, or vice versa) and cannot be consistently predicted, the current code philosophy is to provide all new low-rise homes with an air-barrier encompassing the foundation walls and floor slab, a Heat Recovery Ventilator (HRV) for air dilution purposes, and a sub-slab rough-in pipe whereby an extraction system may be connected if post-occupancy testing reveals radon levels in excess of 200 Bq/m3. It should be noted that these requirements are found within the OBC, and applicable not only in Ottawa but across the province.
Planning (subdivision or site plan) processes do not typically speak to radon, because radon mitigation is handled through the downstream building permit & inspection processes for the new buildings (via the OBC). Existing home and building owners (whether in proximity to sites undergoing civil or building construction, or not) are encouraged to test their buildings using a 3-month test kit to ensure their buildings do not have elevated radon levels. If the testing reveals concentrations more than 200 Bq/m3, they are advised to consult with a certified radon professional on remediation options.