Ontario · rules and data checked October 8, 2026

Home health check for Sudbury

In Health Canada's 2012 survey, 5.1% of 97 homes tested in the Sudbury and District Health Unit region were above the 200 Bq/m³ radon guideline. Sudbury's January averages −13.0 °C (ECCC), with about 88 nights a year below −10 °C, when CMHC advises keeping indoor humidity near 30% to stop window condensation. Ontario requires carbon monoxide alarms in existing houses.

Radon, 2012 survey

5.1%

above 200 Bq/m³ (97 homes)

Radon, 2024 survey

—

no figure for this area

January average

−13.0 °C

88 nights a year below −10 °C

Private wells

Some

in Sudbury

Home health check for Sudbury

Four quick checks, set up with Sudbury's winter temperatures and Ontario's alarm rules. Change any value; nothing you enter leaves your browser.

Radon test result

Example value: the Health Canada guideline. Replace it with your own result from a test of at least 3 months.

200Bq/m³ (5.4 pCi/L)

Scale to 800 Bq/m³. 1 pCi/L = 37 Bq/m³.

At the guideline. Health Canada's guideline is 200 Bq/m³; it advises keeping radon as low as reasonably achievable, so consider retesting in the heating season.

Health Canada's lifetime lung cancer risk: for a never-smoker about 1% at low radon, 2% after lifetime exposure at 200 Bq/m³ and 5% at 800; for a smoker 12%, 17% and 30%. Only a test of 3 months or longer gives an annual average; short tests can mislead.

Winter humidity and window condensation
°C
%
Outdoor temperature

January average: ECCC 1981–2010 normals. Cold snap: NRCan's HOT2000 winter design temperature for Sudbury.

47%highest humidity before the glass fogs at −13.0 °C

Double glazing, clear (1970s–1990s) (U 2.86): condensation starts at about −20.1 °C outside with 40% humidity inside.

The centre of the glass stays dry at −13.0 °C. It is about 9.3 °C, above the 6.9 °C dew point. The bottom edge and frame run colder, so condensation can start there first.

CMHC: when it is below −10 °C outside, keep indoor humidity at about 30%, and as low as 25% in extremely cold regions. Sudbury averages 88 nights a year below −10 °C.

Smoke and carbon monoxide alarms

A sleeping area is a group of bedrooms off one hallway.

Smoke alarms required by law
3
Smoke alarms for full coverage (new-home standard)
6
CO alarms recommended
2

Required: at least 3 under Ontario rules.

“Full coverage” follows the National Building Code for new homes: one on every storey including the basement, one in each bedroom and one outside each sleeping area, interconnected. CO: NRCan advises one near the furnace or other fuel-burning appliance and one in each bedroom area.

Mould: clean it yourself or call a pro?

Example values shown. 1 m² is about 10.8 sq ft.

Small: you can clean it yourself if you are healthy.

Up to three patches, each under 1 m²: clean with water and unscented dish detergent, wearing safety glasses, an N95 mask and rubber gloves (CMHC). People at risk from mould should not clean it.

Fix the moisture source first. Testing for mould types is usually unnecessary (Health Canada). You entered 2 patches, the largest about 0.5 m².

Sudbury at a glance

Radon surveys covering Sudbury
SurveyResult
Health Canada, 2012Sudbury and District Health Unit, 97 homes, long-term tests5.1% above 200 Bq/m³; 1.0% above 600

The 2024 survey pools long-term tests that households volunteered, so it is not a random sample, and more tests were in basements than in 2012. Health Canada's guideline: fix a home above 200 Bq/m³ within a year. Test kits cost about $30–$80 including the lab; mitigation about $2,000–$3,000.

Highest indoor humidity before windows fog (21 °C inside)
WindowAt −13.0 °CAt −27.7 °C
Single glazing with a storm windowU 2.946%32%
Double glazing, clear (1970s–1990s)U 2.8647%33%
Double glazing, low-e and argon (2000s)U 1.862%50%
ENERGY STAR (U 1.22 or better)U 1.2273%63%
Triple glazingU 1.469%59%

Centre of the glass, from the National Building Code's indoor air film and the Magnus dew point formula. January average from ECCC normals; the cold-snap column is NRCan's winter design temperature. Window edges fog sooner, so follow CMHC: about 30% humidity below −10 °C, which Sudbury sees on about 88 nights a year.

Smoke alarms in Ontario

Ontario Fire Code Div. B 2.13.2.1: an alarm in the hallway serving sleeping areas (or between the sleeping area and the rest of the home if there is no hallway), and on each storey without a sleeping area, so in practice every storey. Alarms may be hardwired (no disconnect switch) or battery-operated, and must meet CAN/ULC-S531.

Existing homes must have them: Yes · Every storey: Yes · In each bedroom: No · Interconnected: No

Law: Ontario Fire Code, O. Reg. 213/07, Div. B Section 2.13 and Subsection 6.3.3 (consolidation period from 2026-01-01; last amendment O. Reg. 303/25)

Official source ↗

Carbon monoxide alarms in Ontario

The Ontario Fire Code requires CO alarms in existing homes, not just new builds. The rule came into force 2014-10-15 (O. Reg. 194/14), with compliance required by 2015-04-15 for buildings with six or fewer suites and by 2015-10-15 for larger buildings. At that point alarms were required next to each sleeping area. O. Reg. 87/25 (filed 2025-06-04) replaced Section 2.16 effective 2026-01-01. Alarms are now required next to each sleeping area AND on every storey without a sleeping area. Hardwired, battery or plug-in alarms are all allowed. The homeowner is responsible in an owner-occupied home and the landlord in a rental. The section does not apply to a building whose CO alarms were installed under the Building Code as it read on or after 2025-01-01.

Official source ↗

Well water in Sudbury

The City of Greater Sudbury says some homes are not connected to public watermains and instead get their water from a private well.

  • Bacteria: At least 3 times a year: spring, summer and fall (local health units, e.g. Ottawa); the province says only 'test regularly' (Free (Public Health Ontario))
  • Chemistry: Not stated by the province, Public Health Ontario or Ottawa Public Health (all checked 2026-10-08). PHO tests bacteria only.

Ontario source 1 ↗ Ontario source 2 ↗ Ontario source 3 ↗

Radon help in Ontario

New homes: Yes. The 2024 Ontario Building Code (in effect Jan 1, 2025, with a grace period to Mar 31, 2025 for designs already substantially complete) requires every new house, including additions, to include a soil-gas barrier and a rough-in for a subfloor depressurization system, under Division B Subsection 9.13.4 (Soil Gas Control); SB-9 is an alternative route for the soil-gas barrier.

Test kits: No province-wide free kit program found. Many Ontario public libraries lend digital radon monitors free with a library card (e.g. Hamilton, Vaughan, Guelph, Kingston Frontenac, Greater Sudbury, Thunder Bay, Brantford, Waterloo), and some health units or municipalities run limited free-kit drives, per Take Action on Radon listings checked Sept 2026.

Other help: Tarion new-home warranty covers radon remediation for 7 years from possession when a long-term test (3+ months) exceeds 200 Bq/m3 (maximum coverage $50,000 for purchase agreements signed after Feb 1, 2021). Low/moderate-income households can apply to the Canadian Lung Association's Lungs Matter program for up to $1,500 toward mitigation (Ontario income cap $105,100).

Find a C-NRPP certified measurement or mitigation professional at c-nrpp.ca. Data checked October 8, 2026.

Common questions in Sudbury

How common is radon in Sudbury?

Health Canada's 2012 survey found 5.1% of 97 homes tested in the Sudbury and District Health Unit region at or above 200 Bq/m³. Neighbouring houses can differ a lot, so the only way to know is a long-term test of at least 3 months, ideally in the heating season.

What indoor humidity should I keep in winter in Sudbury?

Health Canada and CMHC advise 30% to 50%, and CMHC says to keep it at about 30% when it is below −10 °C outside (as low as 25% in extreme cold). Sudbury averages 88 nights a year below −10 °C. At the January average of −13.0 °C, clear double-glazed windows start to fog at about 47% humidity at the centre of the glass, and at about 33% in a cold snap of −27.7 °C; the edges fog sooner.

How many smoke alarms does a house need in Ontario?

Ontario Fire Code Div. B 2.13.2.1: an alarm in the hallway serving sleeping areas (or between the sleeping area and the rest of the home if there is no hallway), and on each storey without a sleeping area, so in practice every storey. Alarms may be hardwired (no disconnect switch) or battery-operated, and must meet CAN/ULC-S531. New homes built to the National Building Code need hardwired, interconnected alarms on every storey and in every bedroom, which is the standard we recommend for full coverage.

Are carbon monoxide alarms required in Ontario?

The Ontario Fire Code requires CO alarms in existing homes, not just new builds. The rule came into force 2014-10-15 (O. Reg. 194/14), with compliance required by 2015-04-15 for buildings with six or fewer suites and by 2015-10-15 for larger buildings. At that point alarms were required next to each sleeping area. O. Reg. 87/25 (filed 2025-06-04) replaced Section 2.16 effective 2026-01-01. Alarms are now required next to each sleeping area AND on every storey without a sleeping area. Hardwired, battery or plug-in alarms are all allowed. The homeowner is

How often should I test my well water in Ontario?

Bacteria: At least 3 times a year: spring, summer and fall (local health units, e.g. Ottawa); the province says only 'test regularly'. Bacteria test cost: Free (Public Health Ontario). The City of Greater Sudbury says some homes are not connected to public watermains and instead get their water from a private well.

How we calculate this

Radon

1 pCi/L = 37 Bq/m³ (Health Canada). The Canadian guideline is 200 Bq/m³; above it Health Canada recommends fixing your home within 1 year, sooner the higher the level. Only a long-term test (at least 3 months, ideally in the heating season) tells you your annual average.

Window condensation

glass temperature = indoor − U × (indoor − outdoor) ÷ 8.33

8.33 W/m²·°C is the indoor air film from the National Building Code (RSI 0.12). The dew point comes from the Magnus formula the US National Weather Service publishes; condensation forms when the glass is colder than the dew point. These are centre-of-glass figures: the bottom edge and metal frames run colder, which is why we show CMHC's simpler rule beside them (30% indoor humidity when it is below −10 °C outside, as low as 25% in extreme cold).

Smoke and CO alarms

“Required by law” applies your province's fire code to the layout you enter. “Recommended” is the new-home standard in the National Building Code (an alarm on every storey, in every bedroom and outside sleeping areas) and NRCan's CO advice (one near the furnace or other fuel-burning appliance and one in each bedroom area). Municipal by-laws can add to provincial rules.

Well water and mould

Testing frequencies and lab fees are the ones your province publishes. Mould size categories are Health Canada's and CMHC's: up to three patches each under 1 m² can be cleaned by a healthy homeowner; more than 3 m² needs a professional.

More for Sudbury

Heating and hot water costs in SudburyWhat heating, hot water and air conditioning cost at your local prices, and what each heating system would cost instead.Upgrade payback in SudburySavings, rebates and payback for attic, wall and basement insulation, windows, air sealing and thermostat setbacks.Appliance running costs in SudburyWhat your fridge, dryer, freezer and other appliances cost to run at your local electricity price, and what a newer model saves.
Build your upgrade plan → All home services in Sudbury Radon testing in SudburyCarbon monoxide testing in SudburyWell water testing in SudburyMould testing in SudburyVentilation assessments in Sudbury Ontario rebates and programs

Sources

Prices and programs checked October 8, 2026. Climate: NRCan HOT2000 (Sudbury) for heating and ECCC 1981–2010 normals (Sudbury A) for cooling and temperatures.

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