Alberta has some of the highest radon levels in Canada, and Calgary homes are sealed tight for six months of the year. Radon is odourless, colourless and completely undetectable without a test — and the only test worth trusting runs for at least three months.
Radon is a radioactive gas produced as uranium in soil and bedrock breaks down. It seeps up through foundations — through cracks, construction joints, sump pits, and the gaps around pipes and floor drains — and accumulates indoors. You cannot see it, smell it, or taste it. There is no symptom that tells you your home has it.
It is the second-leading cause of lung cancer in Canada after smoking, responsible for roughly 3,200 deaths a year. Unlike most of the hazards in a home, radon is not a maintenance problem or a construction defect — it comes from the ground the house sits on, which is why a brand-new home can test higher than a century home two streets over.
The good news is that radon is one of the few serious home hazards that is cheap to measure and reliably fixable. A test kit costs less than dinner out. Mitigation, if you need it, is a one-time cost in the low thousands and works permanently.
What this guide will not do is tell you your home is fine. Nobody can tell you that without a test — not us, not your inspector, and not your neighbour's result. What it will do is show you how to test properly, because a badly run test is worse than no test at all: it gives you a number you trust that happens to be wrong.
Alberta sits on geology with meaningful uranium content, and the province consistently records radon levels well above the Canadian average. Prairie soils and the glacial till under much of Calgary allow gas to migrate readily toward the surface — and toward the negative pressure of a heated basement.
Radon concentration is a function of how much gas gets in versus how fast it leaves. For roughly half the year, Calgary homes are sealed shut and heated. Warm air rises and escapes through the upper floors, which draws replacement air in at the lowest point of the house — the basement — pulling soil gas along with it. This is called the stack effect, and it is why the same home will almost always test higher in January than in July.
This surprises people. Modern homes are built far more airtight than homes from the 1960s, which is excellent for heating bills and terrible for radon dilution. A well-sealed 2015 build in a new community can and does test higher than a draughty older home. Age of home tells you nothing about radon risk.
Radon varies enormously house to house, even between homes with identical floor plans on the same street. It depends on the specific soil beneath your foundation, the pathways into your particular basement, and how your home is ventilated. A low reading next door is not evidence about your home — it is a completely separate measurement.
Radon is not a steady number. It rises and falls with barometric pressure, wind, temperature, whether your furnace is running, whether a window was open, and whether it snowed. A reading taken over three days captures three days of weather — not how you actually live in the house.
Two- to seven-day tests can be off from the home's true annual average by a wide margin in either direction. That cuts both ways: a short test can frighten you into mitigating a home that does not need it, or reassure you about a home that does.
Health Canada recommends a long-term test of at least three months — 91 days minimum — using a passive alpha-track or electret detector. That duration averages out the daily and weekly swings and gives you a number that reflects your actual exposure.
Run your test between roughly October and April, when the house is closed up and the furnace is cycling. This is deliberately the worst-case window, and that is the point — you want to know your exposure when it is highest, not when every window has been open for a month. A summer test on a Calgary home routinely understates the winter reality.
Short-term tests are screening tools, not decisions. They have a legitimate role in a real estate transaction, where a 91-day test is impossible inside a condition period — covered in the next section. Treat the result as a flag, not a verdict, and follow up with a proper long-term test after possession.
The detector goes in the lowest level of the home where you spend at least four hours a day. For most Calgary families that is a developed basement — a family room, home office, gym, or bedroom. If your basement is genuinely unfinished storage nobody uses, test the main floor instead. Do not test the crawlspace or an unused mechanical room and then treat that number as your exposure; it will read high and it is not where you breathe.
Put the detector at breathing height — roughly one metre off the floor — and at least 50 cm away from exterior walls, 20 cm from any other object, and well clear of windows, doors, vents, fireplaces, and heat sources. Do not put it in a kitchen, bathroom, or laundry room, where humidity and exhaust fans distort the reading. A shelf or bookcase in the middle of a finished basement room is close to ideal.
Do not change how you use the house to make the number look good. Do not crack windows, run extra fans, or leave the basement door open. The test is measuring your ordinary life in the home — if you alter your habits for 91 days, you have measured a house nobody lives in.
Record the exact start and end dates, seal the detector as instructed, and mail it to the lab promptly — the analysis is time-sensitive. Results usually come back within two to three weeks as a single number in becquerels per cubic metre (Bq/m³).
A proper radon test takes 91 days. A Calgary condition period typically runs seven to fourteen. You cannot do a valid long-term test before you have to decide whether to buy the home — and any agent who tells you otherwise is describing a screening test.
First, ask whether the seller has tested. More Calgary sellers have results than you would expect, particularly if they mitigated. If a mitigation system is installed, ask for the post-mitigation test result and the installer's paperwork — a system with no verification test behind it is an unknown.
Second, you can run a short-term screening test during conditions — typically a 48-hour to seven-day device placed by a certified professional, sometimes as an add-on to the home inspection. Understand what you are getting: a snapshot that flags a serious problem but cannot rule one out.
Third, and most practically for most buyers: proceed on the purchase and budget for the possibility. Mitigation is a known, bounded cost in the $1,500–$3,500 range. It is not a reason to walk away from the right home — it is a line item.
If a screening test comes back dramatically high — several times the guideline — that is worth raising during conditions, and worth a conversation about who pays for mitigation. A result modestly over 200 Bq/m³ on a two-day test is not proof of anything and is a weak negotiating position. We will tell you honestly which situation you are in.
Whatever happens during conditions, start a long-term test in your first heating season in the home. This is the number that actually matters, and it is the one almost nobody follows through on.
Health Canada's action guideline is 200 becquerels per cubic metre. Above that level, remediation is recommended, and the guidance is to act within two years — or within one year if you are above 600 Bq/m³.
This is the part people miss. 200 Bq/m³ is an action threshold, not a safety line. Risk is continuous: 190 is not safe and 210 is not dangerous — the risk simply rises with concentration and with years of exposure. The World Health Organization suggests a reference level of 100 Bq/m³, half the Canadian figure. If you test at 120 and have a young family sleeping in the basement, mitigating is a perfectly rational choice even though no rule requires it.
Radon and tobacco smoke are not additive — they compound. A smoker living in a high-radon home carries a substantially greater lung cancer risk than either exposure alone would suggest. If anyone in the household smokes or vapes indoors, treat a borderline result more seriously.
Re-test rather than agonize. A second long-term test in a different room on the same level, or in a subsequent heating season, costs another $50 and gives you a much firmer basis for a $3,000 decision.
The proven fix is Active Soil Depressurization (ASD). A pipe is cored through the basement slab into the gravel beneath it, routed up through the house or along an exterior wall, and fitted with a continuously running inline fan that vents above the roofline. The fan holds the area under the slab at slightly lower pressure than the basement, so soil gas is drawn out and exhausted before it can enter the home.
It is not a filter, and it is not a sealant. It redirects the gas — which is why it works so well and keeps working.
In Calgary, expect $1,500–$3,500 for a typical single-family installation, varying with foundation type, how the pipe has to be routed, and whether you want it concealed. A correctly designed system typically cuts radon by 80–99%, routinely taking a reading of 600 down under 100. Running cost is modest — the fan draws roughly as much power as a lightbulb, plus some conditioned air loss.
Hire a C-NRPP-certified radon mitigation professional. This is a specialty: fan sizing, pipe routing, slab sealing, and exhaust placement all determine whether the system performs. A general contractor coring a hole and mounting a bathroom fan is not mitigation, and badly placed exhaust can pull radon back into the house.
A mitigation system without a follow-up test is an assumption. Run another long-term test after installation to confirm the result, and keep the paperwork — a documented before-and-after is a genuine asset when you sell.
Alberta building code has required new homes to include a radon rough-in since 2015 — a capped pipe stubbed through the basement slab, sitting ready for a fan. Most owners of newer Calgary homes have no idea it is there. Look for a capped vertical pipe in the mechanical room or a corner of the basement, often labelled.
This matters, and builders' sales staff sometimes blur it. The rough-in is plumbing, not protection — with the cap on and no fan, it does nothing at all. It simply means that if you test high, activating the system is faster and cheaper than a retrofit, often in the $800–$1,800 range rather than the full cost.
Airtight new construction and the stack effect mean new Calgary homes frequently test above the guideline. Being new is not a defence, and the code rough-in is not a substitute for a measurement. Run your 91-day test in the first winter after you take possession.
If you are buying new construction, ask the builder where the rough-in terminates and whether they offer to activate it as an upgrade. Getting it done during construction is nearly always cheaper than after drywall and landscaping are in.
Even with a clear result, re-test roughly every five years. Soil conditions shift, foundations develop new cracks, and the ground around a house changes as landscaping and drainage age.
Re-test after a basement development, new windows, a furnace or HVAC replacement, foundation repair, a new sump pit, or significant weatherstripping and air sealing. Anything that changes how air moves through the house can change your radon level — and energy-efficiency upgrades usually push it upward by tightening the envelope.
Confirm the system worked with a long-term test, then re-test every few years to verify it is still performing. Fans do fail. Check the manometer — the small U-shaped pressure gauge on the pipe — a few times a year; if the fluid levels are even, the fan has stopped.
File your test results and any mitigation documentation with your home records. In Alberta, a known radon issue is the kind of thing a seller may need to address on the property disclosure statement, and a documented test with a working system is a far better answer than a shrug.
Health Canada recommends a long-term test of at least three months — 91 days minimum — using a passive alpha-track detector. Radon levels swing daily with weather, pressure and ventilation, so shorter tests can be badly off from your home's true average in either direction. Run the test during the heating season, roughly October through April, when Calgary homes are closed up and levels are at their realistic worst.
Yes, as a screening tool with known limits. In a real estate transaction a 91-day test is impossible inside a seven- to fourteen-day condition period, so a professionally placed 48-hour to seven-day test can flag a serious problem. It cannot clear a home. Treat a short-term result as a flag rather than a verdict and follow up with a proper long-term test after possession.
There is no safe level — risk rises continuously with concentration and years of exposure. Health Canada's action guideline is 200 Bq/m3, above which remediation is recommended within two years, or within one year above 600 Bq/m3. The World Health Organization suggests a lower reference level of 100 Bq/m3. Many Calgary homeowners reasonably choose to mitigate between 100 and 200, particularly with children or a smoker in the home.
In the lowest level of your home where someone spends at least four hours a day — usually a developed basement. Place it about one metre off the floor, at least 50 cm from exterior walls and 20 cm from other objects, away from windows, doors, vents, fireplaces and heat sources. Never test in a kitchen, bathroom, laundry room, crawlspace, or an unfinished utility room nobody uses.
Yes, and they frequently test high. Modern airtight construction reduces the natural ventilation that used to dilute radon, so new builds can read higher than older homes. Alberta code has required a radon rough-in in new homes since 2015, but a rough-in is just a capped pipe — it provides no reduction until a fan is installed. Test in your first winter in the home.
A typical single-family Active Soil Depressurization system runs $1,500–$3,500 installed, depending on foundation type and pipe routing. If your home has a code rough-in already in place, activating it is often $800–$1,800. A properly designed system reduces radon by 80–99% and costs roughly $60–$150 a year in electricity. Always use a C-NRPP-certified mitigation professional and re-test afterward to confirm it worked.
Only a short-term screening test, which many Calgary home inspectors offer as an add-on. It cannot give you a reliable annual average. The more useful steps during conditions are asking whether the seller has ever tested, requesting post-mitigation results if a system is installed, and budgeting $1,500–$3,500 as a contingency. Mitigation is a bounded, fixable cost and rarely a reason to walk away from the right home.
No. Radon varies dramatically between adjacent homes, even identical floor plans on the same street, because it depends on the specific soil beneath your foundation, the entry points into your basement, and how your home is ventilated. A low reading next door is not evidence about your house. The only way to know your level is to test your own home.
We raise radon on every purchase — before conditions come off, not after. If you are buying, we will tell you honestly whether a screening result is worth negotiating over. If you are selling a mitigated home, that documentation is an asset and we will use it.
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