Radon in Ottawa (2026): What the Data Shows, Why It's High in Some Areas, and What Ottawa Homeowners Should Do

Flat-vector map of Canada with a coral red pin marking Ottawa, Ontario, alongside a circular badge showing 17% — Ottawa-Gatineau Metro share (1 in 6) of homes above the Health Canada radon guideline

A note before you read. This article is general health and home-testing information for Ottawa homeowners, drawn from Health Canada, Ottawa Public Health, Cancer Care Ontario, and the Canadian Cancer Society. It is not medical advice. See full disclaimers at the bottom.

If you live in Ottawa and you've been told radon is "more of a Calgary problem," that's only partly true. Per the Evict Radon National Study, about 1 in 6 Ottawa-Gatineau Metro Area homes test above the Health Canada 200 Bq/m³ guideline — meaningfully higher than the Canadian average. The greater Ottawa Valley contains documented radon hotspots, and Ottawa Public Health publishes its own dedicated radon resource page recognizing radon as an important indoor air quality issue for the National Capital Region.

The good news: Ottawa is in Ontario, which means Ontario new-build owners may also have access to Tarion warranty coverage of up to $50,000 of radon mitigation if their home is within its 7-year warranty window. The Canadian Lung Association's "Lungs Matter" program offers up to $1,500 toward mitigation for eligible Canadians, and Ottawa has a strong C-NRPP-certified mitigator network.

This guide walks through the Ottawa data, explains why some Ottawa areas have meaningfully elevated radon, and lays out the practical step-by-step from "I want to know" to "result in hand."

TL;DR for Ottawa homeowners

  • About 1 in 6 Ottawa-Gatineau Metro Area homes test above the Health Canada 200 Bq/m³ guideline (Evict Radon National Study).
  • The Ontario provincial average is about 8% above the guideline (2012 Health Canada Cross-Canada Survey); Ottawa-area data suggests the local rate is meaningfully higher.
  • Average Ottawa-Gatineau home: about 86 Bq/m³ (Evict Radon).
  • The only way to know your home's level is to test it. Long-term test, 91+ days, ideally during the heating season. Order a $89 long-term radon test kit →
  • Ontario new-build owners may have Tarion warranty coverage of up to $50,000 for radon mitigation. The Canadian Lung Association's Lungs Matter program offers up to $1,500 for eligible homeowners.

Table of contents

  1. What the published Ottawa radon data actually shows
  2. Why Ottawa radon is elevated in some areas — geology and construction
  3. What to do as an Ottawa homeowner
  4. Tarion warranty coverage for Ottawa new-build owners
  5. Local Ottawa and Ontario resources
  6. FAQ — Ottawa-specific questions
  7. Disclaimers
  8. Sources

What the published Ottawa radon data actually shows

Ottawa's residential radon profile is documented through several sources:

  • Evict Radon National Study: about 1 in 6 Ottawa-Gatineau Metro Area homes test above the 200 Bq/m³ guideline, with an average residential level of about 86 Bq/m³.
  • Ontario provincial average (2012 Cross-Canada Survey): about 8% of homes above the guideline (Health Canada).
  • Cancer Care Ontario notes that radon risk varies significantly across Ontario, with the Ottawa region falling in the higher-risk category.
  • Older Ottawa-specific research has reported arithmetic mean radon concentrations around 120 Bq/m³ with about 12% of Ottawa homes above 200 Bq/m³.
  • Ottawa Public Health maintains a dedicated radon resource page, recognizing radon as an important indoor air quality concern for the National Capital Region.

Sources: Evict Radon National Study; Ottawa Public Health; Cancer Care Ontario

The takeaway: Ottawa is not a low-radon city. Roughly one in six Ottawa-Gatineau homes has radon levels Health Canada considers worth acting on, the broader Ottawa Valley contains documented hotspots, and the only way to know your specific home's level is a long-term radon test.

Order a $89 long-term radon test kit →

Why Ottawa radon is elevated in some areas — geology and construction

Three factors influence Ottawa's residential radon profile:

1. Geology. Ottawa sits at the southern edge of the Canadian Shield, with the Ottawa River separating the Shield (to the north and northwest) from the St. Lawrence Lowlands sedimentary basin (to the south and east). Areas of the greater Ottawa region underlain by uranium-bearing Shield bedrock — including parts of the Ottawa Valley extending west and north — show measurably higher residential radon than areas underlain by sedimentary rock. This means radon levels can vary substantially across Ottawa neighbourhoods depending on local geology.

2. Climate. Ottawa has a long heating season — typically October through April — with cold winter temperatures that lead to homes being sealed against the weather. Furnaces and HVAC systems run regularly, and the natural "stack effect" (warm air rising through the home creating negative pressure at the lowest level) actively pulls soil gas into basements.

3. Building construction. Ottawa's housing stock is dominated by single-family homes with full basements, often with finished basement living areas (rec rooms, home offices, basement bedrooms, in-law suites). Modern Ottawa construction emphasizes energy efficiency — tighter building envelopes that retain indoor radon.

The combination — variable Ontario geology with documented Ottawa Valley hotspots + a long heating season + finished-basement housing stock — is why Ottawa shows meaningfully elevated residential radon despite the lower Ontario provincial average.

What to do as an Ottawa homeowner

Step-by-step:

Step 1: Test (long-term, 91+ days). Health Canada's recommended test for a homeowner mitigation decision is a long-term alpha-track lab test, deployed for at least 91 days during the heating season (October–April in Ottawa), in the lowest lived-in level of your home. The test costs $89 all-in with RadonTest.ca — kit, tracked outbound, prepaid tracked Canada Post return label, and analysis at Lex Scientific in Guelph, Ontario (a C-NRPP-listed Canadian lab).

Step 2: Read your result. Below 200 Bq/m³, no mitigation is required (Health Canada recommends retesting every 5 years). Above 200 Bq/m³, mitigation is recommended. See our How to Read Your Radon Test Results and What to Do If Your Radon Level Is Above 200 Bq/m³ guides.

Step 3: Mitigate, if needed. A C-NRPP-certified mitigation contractor installs a sub-slab depressurization system at a typical Ontario cost of $2,500–$4,500. These systems typically reduce radon by up to 95% (Health Canada cites reductions of more than 80%; CARST cites up to 95%). Find an Ottawa-area C-NRPP-certified mitigator via the C-NRPP Find a Professional tool.

Step 4: Apply for Tarion warranty coverage (if applicable) AND/OR the Lungs Matter grant. See the Tarion section below for new-build details. The Lungs Matter program offers up to $1,500 for eligible Canadians.

Step 5: Verify. Once mitigation is complete, run an independent post-mitigation test to confirm levels are below 200 Bq/m³ and stay that way.

Order your Ottawa kit — $89 →

Tarion warranty coverage for Ottawa new-build owners

Ontario is one of the only places in Canada whose statutory new-home warranty covers radon — and Ottawa, being in Ontario, is fully covered by the program.

Tarion's radon coverage (Tarion):

  • Coverage amount: Up to $50,000 for new-home Agreements of Purchase and Sale signed on or after February 1, 2021 (up to $15,000 for APSes signed between March 25, 2013 and January 31, 2021).
  • Coverage period: 7 years from possession.
  • Trigger: A long-term test (≥3 months) using a C-NRPP-certified device, with lab analysis, in the basement (not crawl space), showing radon above 200 Bq/m³.
  • The warranty travels with the home to subsequent owners — if you bought a resale Ottawa home that's still within its 7-year window, you may inherit the remaining coverage.

If you're an Ottawa new-build owner or recent buyer, our full Tarion radon warranty claim guide walks through the claim process step-by-step.

Note: Meeting the test-type criteria is one of several conditions for a Tarion claim — see the full guide for the complete requirements.

Local Ottawa and Ontario resources

  • Ottawa Public Health — Radon in Your Home (ottawapublichealth.ca) — the City's public-health radon resource page
  • Cancer Care Ontario — Risk of Residential Radon Exposure (cancercareontario.ca)
  • Tarion — Radon warranty coverage (tarion.com) for Ontario new-build owners
  • Take Action on Radon — Ontario (takeactiononradon.ca/provinces/ontario)
  • Canadian Lung Association — Lungs Matter mitigation grant (lung.ca)
  • C-NRPP Find a Certified Professional (c-nrpp.ca) — Ottawa-area certified measurement and mitigation professionals

Note on Ontario building code. New-build Ottawa homes are subject to the 2024 Ontario Building Code, which requires a Level 1 radon "rough-in" (capped vent pipe through the slab + soil gas barrier + sealed perimeter).

Note on Ontario real estate disclosure. Ontario uses OREA's Form 220 (Seller Property Information Statement, "SPIS"). SPIS use is voluntary, but once a seller has tested or completed the form, the duty to answer truthfully and the latent-defect doctrine apply. See our Real Estate Radon Guide.

FAQ — Ottawa-specific questions

How common is high radon in Ottawa? Per the Evict Radon National Study, about 1 in 6 Ottawa-Gatineau Metro Area homes test above the Health Canada 200 Bq/m³ guideline. The Ontario provincial average from the 2012 Cross-Canada Survey is about 8% — Ottawa is meaningfully higher than the Ontario average. The only way to know your home's specific level is to test it.

Why is Ottawa higher than the rest of Ontario? Ottawa sits at the southern edge of the Canadian Shield, which contains uranium-bearing bedrock that produces meaningfully higher background radon than the sedimentary rock under southern Ontario. Some Ottawa-area neighbourhoods — particularly those underlain by Shield bedrock to the north and west — show notably elevated levels.

Are some Ottawa neighbourhoods worse than others? Yes — Ottawa's geology varies substantially across the city, with Shield-influenced areas (northern and western Ottawa, the Ottawa Valley extending west) generally showing higher rates than St. Lawrence Lowlands areas (south and east). That said, individual home levels vary substantially even within neighbourhoods, and the only way to know your specific home's level is to test it.

Does my newer Ottawa home have a radon rough-in? If your home was built under the 2024 Ontario Building Code (in force January 1, 2025) or the prior 2012 Ontario Building Code (which required a rough-in only in three designated areas, not Ottawa), the answer varies. New homes built since January 2025 anywhere in Ontario, including Ottawa, must have a vent pipe rough-in. See our Canadian Building Codes guide.

Can I claim Tarion warranty coverage if my Ottawa home tests above 200 Bq/m³? Possibly. If your home is in its 7-year Tarion warranty window from the original possession date, and you have a qualifying long-term test result above 200 Bq/m³, you may be able to claim up to $50,000 of Tarion-covered mitigation (for Agreements of Purchase and Sale signed on or after February 1, 2021). See our full Tarion radon warranty claim guide for the step-by-step process and complete requirements.

How much does radon mitigation cost in Ottawa? Typical Ontario residential mitigation costs are $2,500–$4,500 for a sub-slab depressurization system installed by a C-NRPP-certified contractor. For Ottawa new-build owners within their Tarion warranty window with a qualifying test, mitigation cost may be substantially or fully covered by Tarion. Otherwise, the Canadian Lung Association's Lungs Matter program may offset up to $1,500.

Where can I buy a long-term radon test kit in Ottawa? You can order a RadonTest.ca $89 all-in long-term kit online and receive it within a few business days anywhere in the Ottawa area — kit + tracked outbound + prepaid tracked Canada Post return label + analysis at a C-NRPP-listed Canadian lab.

Do I have to disclose elevated radon when I sell my Ottawa home? Ontario uses OREA's Form 220 (SPIS), which is voluntary but, once completed, requires truthful answers. Independent of the SPIS, the latent-defect doctrine applies under common-law principles, and a known elevated radon reading is generally treated as a material defect requiring disclosure. See our full Real Estate Radon Guide.

When is the best time of year to test in Ottawa? The heating season — October through April — produces the highest indoor radon levels and is the recommended testing window per Health Canada. A long-term test (91+ days) started in early October gives you a strong heating-season reading.

Where can I find a C-NRPP-certified radon mitigator in Ottawa? The C-NRPP Find a Certified Professional directory lists certified measurement and mitigation professionals by area.

Test your Ottawa home — $89, all in

About 1 in 6 Ottawa-area homes test above the Health Canada radon guideline, the Ottawa Valley contains documented hotspots, and the action item is clear: a long-term radon test that produces a real lab result. For new-build Ottawa homeowners, that lab result may also support a Tarion warranty claim of up to $50,000.

RadonTest.ca — $89 all-in (plus applicable tax). Long-term 91-day alpha-track test kit. C-NRPP-listed device. Analysed at Lex Scientific in Guelph, Ontario — Canadian lab, C-NRPP listed, ISO/IEC 17025 accredited by CALA. Tracked Canadian shipping both ways. Written lab report PDF delivered to your inbox.

Order — $89 →

Important disclaimers

Not medical, legal, or warranty advice. This article provides general health and home-testing information for Ottawa homeowners drawn from publicly available Health Canada, Ottawa Public Health, Cancer Care Ontario, Tarion, Canadian Cancer Society, and Evict Radon National Study materials. It is not medical advice, legal advice, or warranty advice. Consult a qualified professional for specific decisions.

Statistics and citations. The 1-in-6 Ottawa-Gatineau figure and 86 Bq/m³ average are from the Evict Radon National Study. Ontario provincial figures are from Health Canada's 2012 Cross-Canada Survey of Radon Concentrations in Homes. National figures are from Health Canada's Radon: What You Need to Know fact sheet (2025). Health Canada updates published figures periodically; figures cited reflect the sources as of May 2026.

Local Ottawa data. Statements about Ottawa radon levels reflect published research, Ottawa Public Health, and Cancer Care Ontario materials. Radon levels vary substantially even between adjacent homes; community-level statistics do not substitute for a home-specific long-term test.

Mitigation cost. The $2,500–$4,500 mitigation cost range is a typical Ontario residential figure. Actual costs vary by home, foundation, complexity, and contractor.

Tarion qualification. Statements that the alpha-track test "qualifies" or "meets Tarion test-type criteria" mean only that the test method matches Tarion's published test requirements. They are not a representation that any specific home, test, or claim will be approved. A complete Tarion radon warranty claim requires several conditions — see our Tarion claim guide and tarion.com for the complete requirements. RadonTest.ca is independent from Tarion.

Lungs Matter grant. Eligibility, grant amounts, and program availability for the Canadian Lung Association's Lungs Matter program may change. Verify directly at lung.ca before relying on the program.

Real estate disclosure. Statements about Ontario real estate disclosure reflect general OREA / common-law latent-defect principles. Specific obligations for any individual transaction depend on the facts; consult an Ontario real estate lawyer.

No diagnosis or treatment claims. RadonTest.ca sells radon test kits. We do not diagnose, treat, or prevent disease.

No warranty as to completeness. RadonTest.ca makes no warranty as to the completeness or accuracy of the information herein and accepts no liability for decisions made in reliance on this article.

Sources & further reading

Ottawa- and Ontario-specific

Health Canada / national

National associations and grants

Related RadonTest.ca articles