When it comes to building radon safe, smart construction starts where few ever look—beneath the slab.
Radon is a naturally occurring radioactive gas. It’s invisible, odorless, and tasteless—but dangerously real. It’s the second leading cause of lung cancer across North America, and the #1 cause among non-smokers. It enters buildings through cracks and gaps in the foundation, quietly accumulating to harmful levels in basements and lower levels.
The good news? Builders have the power to stop it—starting with better below-grade practices.
What Is Radon? (And Why You Need To Be Radon Safe)
Radon forms naturally in the ground as uranium in soil and rock breaks down. Outdoors, it dissipates harmlessly into the air. But when it finds its way into enclosed buildings—especially homes—it can concentrate to levels that pose a serious long-term health risk.
Key Characteristics of Radon:
- Invisible & Odorless: Radon cannot be detected by human senses. You won’t see it, smell it, or taste it.
- Naturally Occurring: It’s produced by the radioactive decay of uranium in nearly all soils and rocks.
- Present Everywhere: Every home has some radon. The concern is when levels indoors climb beyond safe thresholds.
How Are People Exposed to Radon?
Radon typically enters homes from the soil below. It seeps in through cracks in foundation slabs, gaps around service pipes, construction joints and sump pits or crawl spaces.
The highest radon levels are often found in basements or ground-floor rooms, especially in homes that are well-sealed or poorly ventilated. In some cases, radon can also be released from well water or certain building materials—but soil gas entry is by far the most significant source.
The Dangers of Radon Exposure
When radon gas is inhaled, it breaks down into radioactive particles called radon progeny. These particles can lodge in the lungs, where they emit ionizing radiation that damages lung tissue at the cellular level.
Short-Term vs. Long-Term Effects
- Short-Term: No immediate symptoms. Radon exposure is undetectable without a test.
- Long-Term: Extended exposure damages lung tissue, increasing the risk of cancer—especially for smokers or those with prior lung conditions.
Radon and Lung Cancer: The Stats That Matter
- #1 cause of lung cancer in non-smokers
- #2 cause overall in Canada and the U.S.
- ~21,000 deaths annually in the U.S. (EPA)
- ~3,200 deaths annually in Canada (Health Canada)
High-Risk Radon Areas in Canada (with Code Requirements)
While Health Canada recommends testing every home, these regions show elevated risk—and building codes are responding accordingly:
Alberta
Consistent radon elevation in Calgary, Edmonton foothills, and southern regions.
Code: Province-wide requirement for passive radon rough-ins in all new homes.
British Columbia
Interior cities like Kamloops and Prince George have high radon potential.
Code: Rough-ins required in high-risk areas per BC Building Code and Health Canada maps.
Manitoba
Nearly 25% of homes test above the national guideline. Central and southern regions see extreme highs.
Code: Requires active radon mitigation systems in high-risk zones.
New Brunswick
About 1 in 4 homes exceed safe levels. High readings common in both rural and urban areas.
Code: Requires active mitigation systems in radon-prone zones.
Nova Scotia
Elevated levels found in granite-based regions like Halifax, Truro, and the Annapolis Valley.
Code: Follows NBC 2015; local enhancements may apply in high-risk regions.
Ontario
High-risk pockets in Ottawa Valley, Sudbury, and Kitchener-Waterloo.
Code: Radon rough-ins required since 2017 in designated high-risk areas.
Quebec
Risk areas include Laurentides, Gaspé Peninsula, Thetford Mines, and Abitibi.
Code: Mitigation provisions included for high-radon zones in provincial building code.
Saskatchewan
Over 50% of homes in some areas exceed 200 Bq/m³. Southern region particularly affected.
Code: NBC 2015 passive mitigation rough-ins followed. Local enforcement may vary.
Yukon
Roughly 1 in 5 homes exceed the guideline, especially around Whitehorse.
Code: NBC compliance; radon resistance strongly encouraged in known high-exposure zones.
Other Provinces/Territories
All follow NBC radon provisions; many recommend radon rough-ins even outside mapped high-risk areas.
High-Risk Radon Areas in the United States (with Code Requirements)
The U.S. follows a state-driven model, but the EPA Radon Zone Map guides most local and state responses. Here’s how high-risk areas are addressing mitigation:
Colorado
Mountain towns like Boulder and Fort Collins show consistently high radon levels.
Code: No statewide mandate. RRNC encouraged in Zone 1 counties.
Illinois
High radon levels in northern and central areas, including suburbs of Chicago.
Code: Passive radon systems required in many new homes.
Iowa
Entire state is a known high-risk Zone 1 area.
Code: Some local ordinances enforce RRNC; broader mandates under consideration.
Kentucky
High radon in Appalachian Plateau and eastern counties.
Code: No statewide requirement, but EPA-recommended practices widely followed.
Minnesota
Glacial soils contribute to high radon in central and northern zones.
Code: Statewide mandate for passive systems in new residential construction.
North Dakota
High average indoor radon due to glacial and shale soil composition.
Code: No state-level code; mitigation encouraged in new builds.
Ohio
Most counties in Zone 1, especially in areas with glacial or shale-based soils.
Code: No statewide requirement; RRNC best practices recommended.
Pennsylvania
Particularly high readings in the Appalachian and Reading Prong regions.
Code: Varies by county; local adoption of RRNC guidelines common.
Utah
The Wasatch Front shows consistently high radon levels.
Code: No state mandate; mitigation advised in Zone 1 locations.
U.S. codes vary widely by state and local jurisdiction. Builders in Zone 1 areas should assume passive systems as a minimum, with accommodations for future active mitigation if levels exceed 4.0 pCi/L after testing.
How Heat-Sheet Heavy Helps You To Be Radon Safe
Heat-Sheet Heavy isn’t just for radiant-ready slabs—it’s a builder’s ally in radon mitigation. With its compressive strength and molded layout grid, it’s the ideal base for integrating sub-slab depressurization systems in both passive and active radon-resistant designs.
- Supports sub-slab venting system layout
- Reduces soil gas entry by improving slab tightness
- Adds thermal and moisture protection under the slab
Builders in high-risk zones across North America are choosing Heat-Sheet Heavy to meet radon requirements while adding efficiency and durability to every build.
Build Better, Breathe Easier
Radon is one of the few health risks that’s both silent and preventable. By designing for it from day one, you help homeowners avoid long-term health consequences—and show your commitment to high-performance, future-ready building.
Whether it’s Kamloops or Kalamazoo, Sudbury or Sioux Falls—Heat-Sheet Heavy lays the groundwork for safer homes.
