How often should you test for radon? Common questions
Sourced answers on when to retest for radon: how often, new homes, after renovations or energy retrofits, and homes that already have a mitigation system.
New homes, renovations and retesting
I live in a brand new home. Do I still need to test?
Yes. New construction does not guarantee a low radon level.
Health Canada recommends two tests for a newly built home. Test during the first heating season after you move in. Then test the home again two years after the year it was built.
My new home has a radon rough-in. Do I still need to test?
Yes.
Soil gas control measures and a rough-in for a subfloor depressurization system make future mitigation straightforward. Health Canada's Radon Reduction Guide says preventive construction measures can reduce the radon entering a home. It also says they do not guarantee that annual average levels will be below the guideline.
Does new construction affect radon levels?
It can. Building design, construction and ventilation all influence indoor radon.
The 2024 Cross-Canada Radon Survey reports research indicating a trend toward higher radon levels in newer Canadian residential buildings. In the survey's Alberta case study, average levels rise with year of construction across roughly five decades.
The survey also says this trend is not universal. In Sweden, a cold climate country like Canada, indoor radon in new buildings has gone down over time. Building age alone does not determine radon level.
I renovated my basement. Should I test again?
Yes, during the next heating season.
Health Canada recommends retesting after any renovation that affects the structure or ventilation of your home. Its examples include renovating a basement, installing a new furnace and adding a bathroom. If your basement was not tested before and is now the lowest lived-in level, Health Canada lists that as a reason to retest too.
Can energy efficiency renovations affect radon?
They can, and Health Canada lists them as a reason to retest.
Health Canada recommends retesting during the next heating season after new windows, insulation or air sealing. The 2024 Cross-Canada Radon Survey describes how this can happen. Tightening a building changes how air moves through it, and if mechanical ventilation is not increased to match, radon-laden soil gas can build up indoors.
The survey raises this as a possible contributor to the rise between the 2012 and 2024 survey results. It points to the uptake of federal and provincial retrofit programs over the past decade. It says energy efficiency does not cause high radon by itself. In Sweden, the most energy efficient houses show the lowest average indoor radon.
When should I retest my home?
Health Canada says to retest in the next heating season after certain changes.
One is a renovation affecting structure or ventilation, such as a basement renovation, a new furnace or a new bathroom. Energy retrofits count too, such as new windows, insulation or sealing. So does major digging beside the home, such as replacing a septic tank, exterior waterproofing, terracing or new drainage.
Retest after new structural damage to the slab or basement walls, or if an untested floor becomes the lowest lived-in level. Retest after a mitigation system is installed, and every five years for an active soil depressurization system. Test a newly built home in its first heating season, and again two years after the year of construction.
My home already has a mitigation system. Do I still need to test?
Yes.
Health Canada recommends testing a home with a mitigation system when there is no recent measurement. These homes usually have lower levels, but they can still be above the guideline and may need more work. Testing is the only way to know whether a system is doing its job. Where an active soil depressurization system is installed, Health Canada recommends retesting every five years.