What Is Radon?
Radon is an odorless, invisible gas that seeps up through the ground and can enter a home through unsealed foundations, cracks in the foundation, gaps in construction materials, and plumbing system components, including sump pumps or drains. Radon gas is also a product of uranium decay. Like uranium, it is radioactive; unlike uranium, it can permeate through rocks or soil, escaping into the air or groundwater. All rocks or soil contain some uranium, but granite, shale, and sandy soils are higher in uranium or radon than clay, limestone, or very moist soil.
Why Is Radon Bad?
Concerns arise when radon gas accumulates in living spaces, as radon is highly carcinogenic. It is the second leading cause of lung cancer, behind smoking, causing over 3,000 deaths per year in Canada – almost eight times more than asbestos.
Where Is Radon Found?
The BC Centre for Disease Control provides a map of certain residential radon testing results across BC, but warns that radon gas levels can vary widely from house to house, even in the same neighborhood.
Cracks in a home’s foundation or bare dirt floors in a crawlspace under the house can provide easy paths for radon to permeate from the soil into living spaces. Due to their improved insulation and airtightness, new homes can accumulate radon gas at even higher levels than older ones. While higher radon levels are found in a home’s basement or lower levels, in apartment buildings or towers, radon gas levels can be higher on the top floors due to the “stack effect” or the rise of warmer air.
How Can You Test for Radon?
The radon level in a home can be measured using commercially available and relatively inexpensive radon test kits. A proper radon test takes at least 90 days to complete and is often recommended to carry out over the winter when homes are more likely to be sealed up. Opening windows and doors, as folks often do in the warmer months, can vent radon gas, yielding false low results. Shorter-term tests are available but are less accurate.
How High Is Too High for Radon Gas Levels?
If radon gas is detected in a living space, remediation measures can be undertaken to lower its levels. The World Health Organization recommends a threshold level of 100 Bq/m3 (or about 3 pCi/L) for initiating remediation measures. In the US, threshold levels of 4 pCi/L (or 148 Bq/m3) require remediation. Health Canada recommends remediation within two years for any homes with radon gas levels exceeding 200 Bq/m3, and within one year for any homes with radon gas levels exceeding 600 Bq/m3.
New Construction Standards
As of March 2024, new homes built in BC are required6 to have a radon gas vent pipe installed to allow the venting of soil gases from the ground beneath the basement or crawlspace to the roof or exterior of the building. This pipe is called a passive sub-slab depressurization system. While often effective at reducing high radon concentrations, a passive sub-slab depressurization system may not bring those concentrations below the guideline levels. The British Columbia Building Code does not require builders to install a fan system in the pipe to turn this into an active sub-slab depressurization system. However, homeowners may wish to install a fan system to reach levels below the recommended threshold.
Retrofitting Older Homes
Older homes can be retrofitted with radon gas mitigation systems that can range from relatively passive methods, such as sealing porous concrete and repairing any cracks in basements or crawlspaces, to more active and costly methods, such as installing a heat recovery ventilation fan in the basement or the whole home or installing a passive or active sub-slab depressurization system like those required in new home construction.
Buying or Selling a Home and Disclosure of Radon Test Results
Property owners are not required to conduct radon testing of their properties. Still, sellers are encouraged to disclose in writing (for example, in the Property Disclosure Statement) whether they have carried out any radon testing and, if so, what the results were.
Since April 2020, Property Disclosure Statements have included the following questions for sellers:
V. To the best of your knowledge, have the Premises been tested for radon?
(i) If yes, when was the most recent test completed and what was the most recent level of radon detected:
Level:_____________ □bq/m3 □pCi/L on ______________________ Date of test (DD/MM/YYYY)W. Is there a radon mitigation system on the Premises?
(i) If yes, are you aware of any problems or deficiencies with the radon mitigation system?