Radon Mitigation in Canada

Active soil depressurization (ASD), more commonly called sub-slab depressurization, is the method Health Canada's consumer guidance names as the most common and effective way to lower indoor radon. A mitigator drills or opens a small penetration through the concrete slab, sets a length of PVC pipe into the aggregate layer below it, and connects that pipe to an inline fan that continuously draws soil gas out from under the foundation and exhausts it above the roofline, away from windows, doors, and air intakes. Lowering the air pressure beneath the slab relative to the air pressure inside the home reverses the pressure differential that pulls radon indoors in the first place, and Health Canada's reduction guide states that this approach can cut radon levels by more than 80% in most homes.

The number of suction points a system needs depends on how the slab is broken up internally. A single open basement slab often needs only one point, while additions, interior footings, and multiple foundation pours can require a second or third pipe run to create an effective suction field under the entire floor area. A qualified mitigator typically performs a diagnostic depressurization test with a temporary fan before finalizing the design, rather than guessing at the layout in advance.

What drives the price

• Foundation type. A single, unfinished basement slab is generally the least expensive case. Slab-on-grade homes, homes with multiple foundation types (basement plus crawlspace), and homes with a sump pit that must be sealed and incorporated into the suction field cost more.
• Finished space. A finished basement adds labour for running pipe through framed walls, closets, or ceilings rather than an open slab, and may require patching drywall or flooring afterward.
• Fan placement and routing. Routing the exhaust pipe through an attic and out the roof is standard, but homes without convenient attic access may need an exterior run up an outside wall instead, which changes both the materials and the labour required.
• Number of suction points. Each additional pipe run adds material and labour cost, and larger footprints or additions are more likely to need more than one.

What C-NRPP certification actually verifies

The Canadian National Radon Proficiency Program certifies individuals under two separate tracks: measurement and mitigation. A mitigation certification confirms that the professional has demonstrated knowledge of radon entry mechanisms, building science, and the CSA-aligned installation standards that govern system design, rather than simply having general HVAC or contracting experience. Working with a C-NRPP certified mitigator matters in practice because an undersized or poorly sealed system can look complete without actually lowering the radon level, and a certified professional's post-installation verification test is what confirms the work was effective rather than cosmetic.

New construction and radon rough-ins

Builders in higher-radon-potential regions increasingly install a passive radon rough-in during construction: a capped vent pipe run from below the slab or vapour barrier up through the structure, positioned so a fan can be added later with minimal disruption if a post-occupancy test comes back elevated. A rough-in costs a fraction of a full retrofit because it uses the same trenching and framing already underway, and several provincial building codes and municipal bylaws in known higher-radon areas now require or strongly encourage it for new residential construction.

Financial assistance and tax treatment

Mitigation is not a universal, income-tested benefit in Canada; support is patchwork and varies sharply by province. The Canada Revenue Agency has formally ruled that radon testing and mitigation system costs, including installation, do not qualify for the federal medical expense tax credit, because they are treated as a capital expense on the home rather than a medical expense under the Income Tax Act, even when a doctor recommends the work. A handful of programs exist below the federal level:

• The Canadian Lung Association's Lungs Matter program provides grants of up to $1,500 toward mitigation for households below a provincial income threshold or a resident diagnosed with lung cancer, conditional on a long-term test result above 200 Bq/m³ and a quote from a C-NRPP certified mitigator.
• Nova Scotia's Radon Reduction Grant Program offers up to $2,500 toward mitigation for eligible low-income households, delivered in partnership with the provincial lung association.
• Manitoba Hydro's Energy Finance Plan provides on-bill financing for mitigation systems with no income threshold, repaid through monthly utility charges rather than a lump sum.
• A small number of municipalities, including Vaudreuil-Dorion, Quebec, reimburse a portion of mitigation costs directly for residents who test through a local program.

Availability changes from year to year, so confirming current terms with a provincial lung association or municipal office before budgeting for a project is worthwhile.

Verifying the fix worked

A mitigation system is not finished the moment the fan is switched on. Health Canada recommends waiting at least 24 hours with the fan running continuously before conducting a follow-up test, and a longer verification test gives a more reliable picture than a same-day spot check. The fan should run continuously going forward, not intermittently, since radon entry does not pause when the system is off. If you have not yet confirmed your baseline level, start with the testing guide, and for background on how the national guideline was set, see the OpenStats indoor radon guide.