Radon in Windsor
Windsor is one of the few places in our service area where the local health unit has published its own radon study.
Windsor radon guide
Radon in Windsor-Essex
Radon testing and mitigation in Windsor-Essex
Windsor’s riverfront neighbourhoods and the Essex County towns along Lake Erie, on flat clay plain between the Detroit River and the lake.
Radon in Windsor-Essex
Windsor-Essex is the southwestern tip of Ontario: the City of Windsor on the Detroit River, then Amherstburg, LaSalle, Tecumseh, Lakeshore, Essex, Kingsville and Leamington across flat farmland and greenhouse country toward Lake Erie. It is also one of the few parts of our service area with its own local radon study. The Windsor-Essex County Health Unit ran Radon: Know Your Level from 2015 to 2018. Across the three years, about 11% of the homes tested were above Health Canada’s 200 Bq/m³ guideline: 18% in Essex County and 6% in the City of Windsor. Neither number is a prediction for your house.
What’s under the ground
Most of Essex County is a flat lake plain: glacial lake clay and silt over till, with sandy beach ridges left by older lake shorelines and limestone and dolostone bedrock close to the surface in places along the Detroit River and the Lake Erie shore. Clay slows soil gas, but it shrinks and cracks in dry summers, and the stone and gravel around a foundation give gas an easy route in.
The health unit reports Essex County higher than the city. Ground, house type and heating all vary at street level, so we treat that gap as a reason to test, not as a map.
The homes
Windsor has a large stock of brick houses from the 1920s through the 1960s in Walkerville, Olde Riverside, Sandwich Town and South Windsor, many with full basements, sump pits and floor drains, all of which are openings for soil gas. Out in the county, new subdivisions in Tecumseh, LaSalle and Lakeshore sit near farmhouses, and converted cottages line the Lake Erie shore around Kingsville and Leamington.
Public health: Windsor-Essex County Health Unit.
What the data says
11%
Of homes tested in the Windsor-Essex County Health Unit’s 2015 to 2018 study were above the 200 Bq/m³ guideline: 18% in Essex County and 6% in the City of Windsor.Source: Windsor-Essex County Health Unit — Radon: Know Your Level, 2015–2018 report
13.8%
Of homes tested in the Windsor-Essex health unit area were at or above 200 Bq/m³ in the Health Canada survey data tabulated by Cancer Care Ontario (2009 to 2013).Source: Cancer Care Ontario — Risk of Residential Radon Exposure Varies Geographically (results by public health unit, Health Canada survey data 2009–2013)
1 in 8
Ontario homes at or above Health Canada’s 200 Bq/m³ guideline in the 2024 Cross-Canada Survey, more than double the share found a decade earlier.Source: Cross-Canada Survey of Radon Exposure in the Residential Buildings of Urban and Rural Communities (2024)
Local factors
Why Windsor-Essex homes should test
Clay plains
Dense clay slows soil gas, but it cracks in dry spells. Gas then follows the easiest route: the gravel backfill, weeping tile and utility trenches that lead straight to a basement.
Shallow or fractured bedrock
Where rock sits close to the surface, as on the Niagara Escarpment or the limestone plains near Lake Erie, joints and fractures can act as pipelines that carry soil gas toward foundations.
Century homes
Fieldstone, rubble and early concrete foundations, earth-floor cellars and open sumps give radon many ways in. Older doesn’t mean safer: these homes still need a test.
New, airtight construction
Canadian research shows newer homes have tended to test higher than older ones. Bigger, taller and tighter homes create a stronger stack effect that draws soil gas in through the slab.
Cottages and crawlspaces
Lakeshore cottages converted to year-round homes often sit on crawlspaces, piers or patched slabs. Once winterized and heated, they can start pulling in soil gas they never did as summer places.
Lived-in basements
Radon is usually highest on the lowest floor. Basement bedrooms, home offices and rental suites mean people spend hours a day where exposure is greatest.
Questions
Radon in Windsor-Essex: common questions
Is radon a problem in Windsor-Essex?
It can be. The Windsor-Essex County Health Unit’s Radon: Know Your Level study (2015 to 2018) found about 11% of homes tested above Health Canada’s 200 Bq/m³ guideline, with 18% in Essex County and 6% in the City of Windsor. Those are study averages, not a prediction for your house. A 91-day test is the only way to know.
Do you serve Amherstburg, Tecumseh, LaSalle and Lakeshore?
Yes. We test and mitigate across the City of Windsor and Essex County, including Amherstburg, LaSalle, Tecumseh, Lakeshore, Essex, Kingsville and Leamington.
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