Short answer
The standard radon fix in Canada is active soil depressurization (also called sub-slab depressurization). A pipe is installed through the basement slab into the gravel below, and a small fan keeps the soil under the house at slightly lower pressure than the indoors. Radon is drawn into the pipe and vented outside instead of entering the home. Properly designed systems typically reduce radon by 90% or more.
Key facts
- Method: active soil depressurization (ASD), per CAN/CGSB-149.12.
- Typical reduction: 90% or more.
- Most installs: one day.
- Running cost: a small fan running continuously, similar to a light bulb or two.
- Suction point
A small pit dug out under a 4–5 inch hole in the slab, where gravel and soil meet the pipe.
- Sealed entry points
The sump gets an airtight lid; major cracks, joints and drains are sealed.
- Vent pipe
Sealed PVC or ABS pipe routed through a closet, chase, garage or exterior wall.
- Manometer
A U-tube gauge on the pipe shows the system is pulling suction, at a glance.
- Fan
Mounted outside the living space (outdoors, in the garage or attic), running continuously.
- Discharge
Released outdoors where it can’t re-enter, clear of windows, doors and air intakes.
How it works
Radon gets into homes because the house is at slightly lower pressure than the soil beneath it. Active soil depressurization flips that relationship. A fan connected to a pipe through the slab pulls air from the gravel and soil under the house, so the area under the slab is at lower pressure than the basement. Instead of soil gas being drawn in through cracks and drains, indoor air is drawn slightly down, and radon is pulled into the pipe and exhausted outside, where it quickly dilutes.
What happens during an install
- Assessment. We look at the foundation, sump, drains, crawlspaces and finished areas, and agree on a pipe route and fan location with you.
- Communication test. We drill small test holes and measure how far suction spreads under the slab. This tells us how many suction points are needed and how big the fan should be.
- Suction point and piping. A core of about 4–5 inches goes through the slab, a small pit is excavated beneath it, and sealed pipe is run to the fan location.
- Sealing. Sump lid, major cracks, floor–wall joints and other accessible openings.
- Fan and discharge. The fan is mounted outside the living space and the exhaust is routed to a safe discharge point.
- Verification. We confirm suction across the slab with pressure readings, label the system, and set up your follow-up test.
Most single-family homes are done in a day.
Other methods, and when they’re used
- Sub-membrane depressurization for crawlspaces and earth floors: a sealed, heavy membrane over the soil with suction beneath it.
- Drain-tile or sump depressurization, using an existing perimeter drain system as the collection layer.
- Block-wall depressurization for hollow concrete block foundations.
- Increased ventilation (for example, a balanced HRV) can help in some homes with moderate levels, but is rarely enough on its own.
- Sealing alone is part of every job but seldom reliable as the only measure.
Running costs and maintenance
- Electricity: radon fans typically draw roughly 20 to 90 watts, running continuously. Expect a modest yearly cost, similar to leaving one or two light bulbs on.
- Heat loss: small. The system pulls a little conditioned air through the slab; good sealing keeps this low.
- Maintenance: glance at the manometer every so often. If the fluid levels even out, the fan may have stopped. Fans usually last many years and are straightforward to replace.
- Noise: with the fan outside the living space and the pipe properly supported, most people don’t notice it.
How you know it worked
Mitigation should be confirmed with measurements, not assumed. A short check after the system has run for at least a day gives an early indication; a long-term test during the next heating season confirms your new average. Re-test every few years and after renovations. Our guarantee: if your follow-up long-term test is at or above 200 Bq/m³, we return and adjust or upgrade the system at no cost.
Who should install it
Health Canada recommends using a professional certified through the Canadian National Radon Proficiency Program (C-NRPP). Certified mitigators design to CAN/CGSB-149.12, Canada’s standard for radon mitigation in existing buildings, and are accountable to the program’s requirements.
Common questions
How much does radon go down after mitigation?
A properly designed and installed active soil depressurization system typically reduces indoor radon by 90% or more.
Can a radon system be installed in a finished basement?
Yes. We usually place the suction point in a mechanical or storage room and route the pipe through a closet, chase, the garage or an exterior wall, so finished spaces stay intact.
Does a radon system need a building permit in Ontario?
Requirements vary by municipality and by what the work involves. We check with your local building department as part of planning, especially for exterior changes on heritage properties.