Why this matters specifically here
Radon comes from uranium decaying in soil and rock, and how much of it ends up in a home's air depends heavily on local geology, not construction quality alone. Health Canada's 2012 Cross-Canada Survey of Radon Concentrations in Homes found Manitoba and Saskatchewan among the provinces with the highest measured rates in the country: about 19% of Manitoba homes and about 16% of Saskatchewan homes tested above the 200 Bq/m3 guideline, roughly two to three times the national average of the time. Follow-up regional testing in specific communities in both provinces has since found pockets considerably higher than those provincial averages. This isn't a reason for alarm on its own, but it is a real, geography-driven reason to take radon seriously here in a way that generic national content usually doesn't reflect.
What radon is, and what the guideline means
Radon is colourless, odourless, and radioactive. It moves through soil and enters buildings mainly through cracks, joints, sump pits, and gaps around foundation penetrations, then gets trapped and concentrated indoors. Health Canada measures it in becquerels per cubic metre (Bq/m3) and sets the action guideline at 200 Bq/m3, averaged over a long-term test (91 days or more) in any area where someone spends more than four hours a day. That guideline has been in place since 2007 and remains current. If a long-term test comes back above it, Health Canada recommends corrective action within a year, sooner the higher the reading.
How a spray foam radon barrier actually works
Closed-cell spray polyurethane foam is one of the few products that does three jobs in a single application: insulation, air barrier, and vapor barrier. Applied at 1½ inches (about R-9 at R-6/inch), it exceeds the National Building Code's under-slab insulation minimum (subsection 9.36) and, at just 1 inch, exceeds air barrier material requirements by roughly 500 times. Because the foam expands about 30 times its volume in seconds, it forms a continuous, unbroken seal across the entire slab area, crushed drainage stone, penetrations, sump pits, and plumbing stacks in one pass, rather than relying on separate membranes, tapes, and caulking at every joint.
The product commonly used for this (CCMC-evaluated 2lb closed-cell foam, such as Grizzly Gold, CCMC 14133L) also resists compression well enough (roughly 28 psi) that crews can walk and work on it without damaging the seal, and it doesn't crack or delaminate the way rigid boards can at joints. On a floating or engineered basement floor with an open earth crawl space beneath it, the same approach is used at greater thickness (2½ inches or more) to fully encase the ground in what amounts to a sealed tub, which is common in older Winnipeg-area homes with open dirt crawl spaces.
What the National Building Code actually requires
NBC subsection 9.13.4 requires new residential construction to include a rough-in for soil gas (radon) control on floors-on-ground: either a gas-permeable layer with an inlet and outlet, or clean granular material and a vent pipe, plus a continuous air barrier system across the floor with all edges and penetrations sealed. The radon vent pipe itself must be at least 100mm in diameter and airtight where it passes through conditioned space. Unless the crawl space beneath a floor is left accessible for a future mitigation system to be installed, new homes and residential buildings must include this rough-in at the time of construction, not as an afterthought. A continuous closed-cell foam application satisfies the air-barrier-system half of this requirement directly, and a thermal break of R-4 to R-10 between the foundation wall and slab (required separately) is a natural byproduct of the same application.
Prevention vs. mitigation: two different jobs
Spray foam radon barrier (prevention)
- When it applies
- New construction, or a basement/crawl space retrofit before or during finishing.
- What it does
- Seals the soil-gas entry pathway at the slab, foundation walls, and every penetration in one continuous, seamless layer, satisfying NBC 9.13.4's air barrier requirement.
- What it doesn't do
- Actively extract or reduce radon that's already concentrated in a home with an unsealed or partially sealed foundation. Prevention, not remediation.
Sub-slab depressurization (mitigation)
- When it applies
- An existing home that has tested above 200 Bq/m3, regardless of what's already sealed.
- What it does
- A fan-driven system draws soil gas from beneath the slab and vents it outside before it can enter the home. Installed by a C-NRPP (Canadian National Radon Proficiency Program) certified mitigation professional. Reduces radon levels 80–99% in the large majority of homes and is considered the gold-standard fix.
- What it doesn't do
- Replace the value of sealing the envelope in the first place; a well-sealed foundation makes any mitigation system that's later needed more effective and lets a smaller fan do the job.
The honest answer for most homeowners: test first (a long-term test kit or a C-NRPP certified measurement professional), then match the response to the number. A spray foam radon barrier during construction or a renovation is one of the most effective preventive steps available. It is not a substitute for testing an existing home, and it is not itself a mitigation system if levels are already elevated.
Frequently asked questions
What radon level is considered safe in Canada?
Health Canada's guideline is 200 becquerels per cubic metre (Bq/m3) as an annual average for areas where someone spends more than four hours a day. This has been the national guideline since 2007. If a long-term test (91 days or more) comes back above that, Health Canada recommends corrective action within a year, sooner at higher readings.
How common is high radon in Manitoba and Saskatchewan?
Health Canada's 2012 Cross-Canada Survey of Radon Concentrations in Homes found about 19% of Manitoba homes and about 16% of Saskatchewan homes tested above the 200 Bq/m3 guideline, both well above the roughly 7% national average at the time. Follow-up regional testing in specific Manitoba and Saskatchewan communities has found even higher rates in some areas. Manitoba and Saskatchewan are consistently named among the provinces with the highest radon exposure in Canada.
Does spray foam alone fix a radon problem?
Not on its own if levels are already high. A closed-cell spray foam radon barrier is a prevention layer: it seals the slab, foundation walls, and penetrations against soil gas entry as part of new construction or a basement retrofit. If a home already tests above 200 Bq/m3, the standard fix is active sub-slab (soil) depressurization installed by a C-NRPP certified radon mitigation professional, which reduces levels 80 to 99% in the large majority of homes. The two approaches work together, not as substitutes for each other.
Basement, slab, or crawl space to seal?
Ask about the Ecologic radon gas barrier system.
