Radon in the Kootenays.
Test First, Then Decide.
The BC Interior is one of three named Canadian radon hotspots. Roughly half of tested homes in Castlegar and Kimberley come back above the action level. A $40 test kit and 91 days of patience tells you where your home stands.
$40, lab fees included. Test October–April for the most accurate reading.
The quick answer
What you need to know in 60 seconds
- Radon is a naturally occurring radioactive gas that seeps out of bedrock. Health Canada’s action level is 200 Bq/m³.
- The BC Interior — including the Kootenays — is one of three Canadian hotspots Health Canada names.
- Of homes tested locally: Castlegar 59%, Kimberley 49–59%, Nelson ~25% were above the action level.
- Radon is the second leading cause of lung cancer in Canada and the leading cause for non-smokers.
- A long-term test kit costs ~$40. Run it October–April for at least 91 days. Lab results in 4–6 weeks.
- If your test is elevated, sub-slab depressurization mitigation runs $2,500–$4,500 in the Kootenays. No provincial or federal rebates.
- Kootenay Energy doesn’t do radon mitigation. We point you to a test kit, and if your result is high, we match you with a vetted local C-NRPP installer.
The local picture
Why Kootenay homes test high
The Kootenay arc sits on uranium-bearing granitic and metamorphic bedrock. As that uranium decays it produces radon — a colourless, odourless gas that follows pressure gradients into homes through floor cracks, sump openings, service penetrations, and unsealed crawlspaces.
Bedrock-source means basement-vs-crawlspace doesn’t predict risk well. A slab-on-grade home with a hairline crack can test as high as a finished basement. The BCCDC interactive radon map renders the regional pattern visually.
| Community | Above 200 Bq/m³ | Source |
|---|---|---|
| Castlegar | 59% | Castlegar Source / My Kootenay Now |
| Kimberley | 49–59% | Kimberley Bulletin (2022/23 + 2023/24 challenges) |
| Nelson | ~25% | BC Lung community testing |
| Greater Fernie | 35% | Regional contractor data |
| Interior BC overall | 8% (provincial avg) up to 29% in named regions | BCCDC, Health Canada |
One caveat on the local percentages: these come from voluntary test-kit challenges, so they over-represent homes whose owners already suspected a problem. Health Canada’s cross-Canada survey puts BC overall at around 8% above the guideline, with up to 29% in certain regions. The truth for any individual Kootenay home is the same either way: you can’t predict, you have to test.
Why it matters
Radon is the second leading cause of lung cancer in Canada
Health Canada attributes about 16% of lung cancer deaths in Canada to radon exposure — roughly 3,200 deaths a year. That’s more than vehicle accidents, carbon monoxide, and house fires combined (Canadian Lung Association). For non-smokers, it’s the leading cause.
Radon and tobacco smoke interact multiplicatively, not additively — a smoker with elevated household radon faces a much higher risk than the two factors added together. Children and adolescents may be more vulnerable due to higher breathing rates and developing tissue.
The dose-response is not zero-threshold. Health Canada uses 200 Bq/m³ as an actionlevel — the point at which mitigation is recommended — not a "safe" level. The World Health Organization recommends acting at 100 Bq/m³, a more conservative bar. Either way, lower is always better, and long-term exposure matters more than any single short reading.
This page is information, not medical advice. For personal risk assessment, consult Health Canada’s radon resources or your physician.
Step one
How to test your home
There are two test types worth considering, and the right one for almost every first-time tester is the cheaper one.
Long-term alpha-track detector — the standard
The kit BC Lung Foundation ships is a Radtrak3 alpha-track detector. You leave it sitting in your lowest occupied level for at least 91 days (12 months is better), then mail it back for lab analysis. Cost is about $40 with lab fees included. This is what Health Canada, BCCDC, and BC Lung all recommend for residential testing.
Electronic monitor — useful for ongoing visibility
Continuous-readout monitors like the Airthings Wave Plus or Corentium Home cost $200–$400 and give you rolling daily readings on an app. The good ones approach C-NRPP-comparable accuracy. Worth it if you want to see the seasonal swing or confirm a mitigation system is doing its job — overkill for a one-time check.
When to test
October through April. Windows are shut, the heat is on, and the stack effect is pulling soil gas up through the foundation harder than at any other time of year. A summer test under-reports because open windows ventilate radon out. Health Canada’s minimum is 91 days; a 12-month test is the most honest single number you can get.
Where to put the detector
Lowest occupied level — wherever you spend at least four hours a day. Roughly a metre off the floor, away from walls, drafts, and direct sunlight. Not in a bathroom, not on top of a heat register. The BC Centre for Disease Control publishes detailed placement protocols if your situation is unusual.
Reading the result
Health Canada’s guidance scales with your number:
- Below 200 Bq/m³: no action required. Re-test every five years or after major retrofit work.
- 200–600 Bq/m³: mitigation recommended within two years.
- Above 600 Bq/m³: mitigation recommended within one year.
A single elevated short-term reading should be confirmed with a long-term test before you commit to mitigation. Short-term variability is real.
If your test is elevated
What mitigation actually does
The dominant method is sub-slab depressurization, often called SSD. The technique sounds more complicated than it is.
A C-NRPP installer drills a 4–5 inch suction point through the basement slab, runs a sealed PVC pipe from below the slab up through the roofline, and adds a small inline fan that pulls air from beneath the foundation and exhausts it above the roof. The fan creates a slight negative pressure under the slab, so soil gas — including radon — vents to outside before it can drift into the home. Health Canada’s Reduction Guidedocuments typical reductions of 80–99%.
Variants for non-standard foundations:
- Sub-membrane depressurization for crawlspaces — same principle, but a sealed plastic membrane covers the dirt and the fan vents from beneath it.
- Block-wall depressurization for hollow concrete-block foundations — less common in Kootenay housing stock.
- HRV-paired ventilation — sometimes used alongside SSD when a home is also pursuing an envelope retrofit. HRV alone rarely solves a serious radon problem.
After the system is installed, a post-mitigation test confirms the result. Most C-NRPP installers include this in the quote — if yours doesn’t, ask why.
Operating cost is small. The fan runs continuously, draws 50–100W, and adds roughly $5–$15 a month to a Nelson Hydro bill. Service life is around 10 years on the fan; the pipe lasts the life of the house.
Real numbers
What mitigation costs in the Kootenays
A typical Kootenay sub-slab depressurization project runs $2,500–$4,500. Health Canada’s national reduction guide cites $2,000–$3,000; local installers tend to start around $2,500–$3,500 for a clean basement install, and complicating factors push the upper end.
What pushes a project toward the top of the range:
- Multiple suction points (large basements, slabs broken up by interior footings)
- Finished basements where drywall and flooring need cutting and patching
- No clean exterior wall path for the vent stack
- Block-wall or membrane systems with extra sealing labour
There are no rebates for radon mitigation in BC.
Not CleanBC ESP. Not HRR. Not FortisBC. Not BC Hydro. Not HomeSave Central Kootenays. The Canadian Lung Association occasionally runs a small means-tested grant ($500–$1,000), but the pool is limited and availability is unreliable. This is a health-driven project that comes out of pocket.
The reason to do it anyway: long-term exposure to elevated radon over a 20–40 year stay in your home is one of the most preventable lung cancer risks you face.
Hiring an installer
Choosing a C-NRPP-certified installer
C-NRPP — the Canadian National Radon Proficiency Program — is the de facto credential for radon mitigation in Canada. Always verify a contractor’s certification number at c-nrpp.ca before hiring. A non-C-NRPP installer can drill a hole and install a fan, but you lose the diagnostic standards, the post-install confirmation testing protocol, and any insurance recourse if the system underperforms.
Radon Boss
Nelson
Nelson, Castlegar, Trail, Kaslo, Creston
West Kootenay Radon
Nelson
Nelson, Castlegar, Trail, Rossland, Salmo, Slocan, Kaslo, Creston
Kootenay Contracting
Cranbrook
East Kootenay (Kimberley, Cranbrook, Fernie) — note: outside RDCK
What to ask before signing a quote
- C-NRPP certification number — verifiable at c-nrpp.ca
- Years operating and approximate number of Kootenay-region mitigations completed
- Is a post-install confirmation test included in the quote?
- Warranty terms on the fan and on workmanship (industry norm: 2 years on workmanship, 5 years on the fan)
- What’s in scope — vent path, fan model, dust and finish restoration, electrical hookup (the latter requires a licensed electrician)
If your test comes back elevated and you’d like a hand-off, we’ll match you with the installer whose service area, current capacity, and approach fits your home. We don’t charge you for that — the installer pays a small referral fee, you pay them their normal rate. That alignment matters: we have no incentive to push you toward a job you don’t need.
If you’re planning insulation or a heat pump, test radon first
Air sealing works by closing the leakage paths that let warm indoor air escape and cold outdoor air enter. Those same paths also let soil gas — radon — vent passively. Tighten the envelope and a marginal radon problem can become a serious one. National Radon Defense and Health Canada both flag concentration increases of 30–60% in some retrofitted homes. It’s why BC’s building code, since March 2024, requires a radon rough-in vent pipe in new homes.
For a Kootenay homeowner planning insulation, air sealing, or a deep-energy retrofit, the order of operations is straightforward.
- Test before work begins. A pre-retrofit baseline is the only way to know whether a future high reading was caused by the work or was always there.
- Mitigate before finishes go in, if needed. Sub-slab depressurization installed before drywall, finished floors, or a sealed crawlspace membrane is faster, less invasive, and noticeably cheaper.
- Re-test after the retrofit. If air sealing pushed an already-marginal home above the action level, you want to know now, not three winters from now.
We add a long-term radon test kit to every retrofit project we scope. Not as a sales add-on — as responsible practice. If the test comes back high, you’re in better hands knowing it now.
Questions
Frequently asked questions
Is radon a problem in Nelson, BC?
Yes. Roughly 25% of tested Nelson homes come back above Health Canada’s 200 Bq/m³ action level. The wider Kootenay region tests higher in some communities — Castlegar and Kimberley both around 59% in their test-kit challenges. The only way to know your home’s number is to test.
How much does a radon test cost in BC?
A long-term BC Lung Foundation test kit runs about $40, lab fees included. If you want continuous readings, electronic monitors (Airthings, Corentium Home) cost $200–$400 for a one-time purchase.
Are there any rebates for radon mitigation in BC?
No. CleanBC ESP, HRR, FortisBC, BC Hydro, and HomeSave Central Kootenays all exclude radon mitigation. The Canadian Lung Association occasionally runs a small means-tested grant ($500–$1,000), but availability is unreliable. Plan for the project as out-of-pocket.
What if my house has a crawlspace, not a basement?
Mitigation still works. The technique is sub-membrane depressurization: a sealed plastic membrane over the crawlspace dirt, with a vent fan pulling soil gas out before it enters the home. C-NRPP installers handle both basement and crawlspace methods.
Will an HRV solve my radon problem?
Sometimes, partially. An HRV can dilute indoor radon modestly, but for homes well above 200 Bq/m³ it usually isn’t enough on its own. Sub-slab depressurization is the dominant solution. For envelope-tight homes, an HRV plus SSD combination is sometimes the right answer — a C-NRPP installer scopes that.
Should I test if I’m planning insulation or a heat pump?
Yes, ideally before the work begins. Air sealing concentrates radon. Without a pre-retrofit baseline, you can’t tell whether elevated post-retrofit levels were caused by the work or were already there. Testing first is cheaper and clearer than testing after.
Does radon come up when buying or selling a home in BC?
It can. BCREA Legally Speaking #577 explains the disclosure considerations for elevated radon during a real-estate transaction. If you’re buying in the Kootenays, asking about a recent test result is reasonable. If you’re selling and have mitigated, keep the receipts and post-install confirmation test on file.
Related reading
Authoritative sources
Health topic — the goal of this page is to point you toward the people whose job it is to be authoritative, not to replace them. These are the sources we cite throughout.
Radon deep-dives
How to test your Kootenay home for radon
Kit options, winter timing rule, and what your number actually means.
Sub-slab depressurization, explained
How mitigation actually works, what it costs in Kootenay homes ($2.5–4.5K), and why HRV alone rarely solves it.
Radon in BC home sales
What buyers and sellers should know — disclosure, testing conditions, mitigation as marketing asset.
Test before insulation or a heat pump
Air sealing concentrates radon by 30–60%. Here's the right sequence to avoid the diagnostic mess later.