Examining the options: Radon mitigation in Canadian homes
Radon is a colorless and odorless natural gas resulting from the decay of uranium, present everywhere in the earth's crust. Outside, the gas is released into the atmosphere where its concentration is of no concern. However, modern construction techniques mean homes are more airtight than before, and radon can be present at higher concentrations.
Radon studies conducted in 2012 in 424 homes in the Kitigan Zibi Anishinabeg First Nation community located in Western Quebec, revealed that 42% of these homes had radon levels above the Government of Canada’s radon guideline of 200 Bq/m3Footnote 1. The Kitigan Zibi Anishinabeg band council took a very proactive stance to reduce radon levels in the affected homes and provide information to local residents about radon mitigation.
In addition to this large-scale successful community radon mitigation program, research was also conducted on the most commonly-used radon mitigation measure, called active soil depressurization. This system works by sucking air (and therefore radon) from beneath the foundation of a home and exhausting it outside. This air is pulled by a fan, and passes through a pipe to move out of the home.
In addition to active soil depressurization, it is possible to reduce radon levels in homes with the addition of a passive radon stack, which doesn’t include a fan but simply provides a passage for the air to be exhausted to the outside.
In 2014, British Columbia became the first province in Canada to mandate for residential construction the installation, in their radon-prone regions, of a passive radon stack extending upwards through the building and ending above the roofline. Theoretically, these can be more effective in cold climates due to the bigger temperature difference between the indoors and outdoors during colder months. However, there has been limited field-testing of passive radon stacks in Canadian homes.
Since 2017, the National Research Council (NRC) Canada and Health Canada conducted comprehensive investigations on the effectiveness of passive radon stacks in reducing radon concentrations in more than 20 homes in Ontario, Quebec and British Columbia. The results so far demonstrate that the passive radon stacks in the tested homes were able to reduce the indoor radon concentration by 40 to 90%. In all the homes with high radon concentrations, the passive radon stacks have been able to reduce the radon concentrations to below the Canadian guideline of 200 Bq/m3.
Recently, the National Research Council’s (NRC) research project team, led by Dr. Liang Grace Zhou (NRC) and Jeff Whyte (Health Canada), has recruited eight newly constructed homes in Kitigan Zibi Anishinabeg First Nation community to join the field study for passive radon stacks. Marcel Brascoupé, owner of MB Radon Solutions, is a radon mitigation professional certified by the Canadian National Radon Proficiency Program who will be working with the research team to install the passive radon stacks in these homes. This radon mitigation measure will be tested between January and December 2020. At the end of the testing period, if the radon levels in these homes remain above the Canadian radon guideline value, the NRC research project will subsidize the conversion of the passive radon stack to an active soil depressurization system by adding a fan to the system and the houses will be re-tested.
This project is a great example to show that radon mitigation systems help keep homes safe.