New Brunswick · rules and data checked October 8, 2026

Home health check for Saint John

In Health Canada's 2012 survey, 10.9% of 101 homes tested in the Region 2 region were above the 200 Bq/m³ radon guideline; the 2024 Cross-Canada survey found 18.4% (1 in 5) of houses at or above 200 Bq/m³ for Saint John, NB. Saint John's January averages −7.9 °C (ECCC), with about 66 nights a year below −10 °C, when CMHC advises keeping indoor humidity near 30% to stop window condensation. New Brunswick has no rule we could confirm for carbon monoxide alarms in existing houses.

Radon, 2012 survey

10.9%

above 200 Bq/m³ (101 homes)

Radon, 2024 survey

18.4%

Saint John, NB

January average

−7.9 °C

66 nights a year below −10 °C

Private wells

Some

in Saint John

Home health check for Saint John

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

Radon test result

Pre-filled with the 2024 Cross-Canada survey's average (geometric mean) for Saint John, NB. Replace it with your own result from a test of at least 3 months.

86Bq/m³ (2.3 pCi/L)

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

Below the guideline of 200 Bq/m³. No action is required. Health Canada still advises keeping radon as low as reasonably achievable, and retesting after major renovations or changes to the basement.

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 Saint John.

53%highest humidity before the glass fogs at −7.9 °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 −7.9 °C. It is about 11.1 °C, above the 6.9 °C dew point. The bottom edge and frame run colder, so condensation can start there first.

Health Canada and CMHC: keep indoor humidity between 30% and 50%. Below −10 °C outside, CMHC advises about 30%; Saint John averages 66 nights a year that cold.

Smoke and carbon monoxide alarms

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

Smoke alarms required by law
1
Smoke alarms for full coverage (new-home standard)
6
CO alarms recommended
2

We couldn't confirm a New Brunswick rule for existing houses; install them anyway.

“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.

Saint John at a glance

Radon surveys covering Saint John
SurveyResult
Health Canada, 2012Region 2, 101 homes, long-term tests10.9% above 200 Bq/m³; 1.0% above 600
Cross-Canada survey, 2024Saint John, NB (Saint John CMA)18.4% (1 in 5) of houses at or above 200 Bq/m³; unweighted geometric mean 86.2 Bq/m³ (report: insufficient information to apply weighting); approx. 300-399 properties with data.

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 −7.9 °CAt −22.5 °C
Single glazing with a storm windowU 2.952%37%
Double glazing, clear (1970s–1990s)U 2.8653%37%
Double glazing, low-e and argon (2000s)U 1.867%54%
ENERGY STAR (U 1.22 or better)U 1.2276%66%
Triple glazingU 1.473%62%

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 Saint John sees on about 66 nights a year.

Smoke alarms in New Brunswick

Regulation 82-20 makes the NFC 2020 a prescribed fire prevention standard, so the NFC rule applies: an alarm between sleeping areas and the rest of the home, battery alarms permitted.

Existing homes must have them: Yes · Every storey: Not confirmed · In each bedroom: No · Interconnected: No

Law: Fire Prevention and Inspection Regulation, N.B. Reg. 82-20 (consolidated to 2025-05-01), s. 2(a)

Official source ↗

Carbon monoxide alarms in New Brunswick

No provincial requirement to install CO alarms in existing homes was found. NB's Fire Prevention Act and its Fire Prevention and Inspection Regulation 82-20 (consolidated to 2025-05-01) contain no CO alarm provision; Regulation 82-20 incorporates the National Fire Code 2020 and National Building Code 2020 as standards. New Brunswick applies the NBC 2020 to construction, alteration and demolition under the Building Code Administration Act.

No official NB statement was found that explicitly confirms or rules out a CO alarm requirement for existing homes, so this is left null. The 2015 announcement that NB would require CO alarms could not be verified from an official source.

Official source ↗

Well water in Saint John

Most of Saint John is on municipal water, but the city's large land area includes rural sections.

  • Bacteria: Twice a year (spring thaw, fall rains)
  • Chemistry: Inorganics at drilling and every 2 years after

New Brunswick source 1 ↗

Radon help in New Brunswick

New homes: Yes. The General Regulation under the Building Code Administration Act (N.B. Reg. 2021-2, as amended) adopts the NBC 2020. NBC 2015 was allowed only for permits issued by Mar 31, 2025. Both include Subsection 9.13.4 soil-gas control with a radon rough-in.

Test kits: NB Lung's "Check Out Radon" program lends free electronic radon screening kits through partner MLA offices, realtors and community health centres, and the GNB radon page (checked Sept 2026) points residents to it. In Oct 2025 New Brunswick also handed out free publicly funded test kits through public libraries, and several libraries ran out within two days; no 2026 round was found.

Other help: GNB says about one in four NB homes exceed 200 Bq/m3 (2024 Cross-Canada Radon Survey). It lists the Homeowner Repair Program and Lungs Matter (up to $1,500; NB income cap $74,600) as possible mitigation help.

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

Common questions in Saint John

How common is radon in Saint John?

Health Canada's 2012 survey found 10.9% of 101 homes tested in the Region 2 region at or above 200 Bq/m³. The 2024 Cross-Canada survey, which pools tests that households volunteered, reports 18.4% (1 in 5) of houses at or above 200 Bq/m³ for Saint John, NB. 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 Saint John?

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). Saint John averages 66 nights a year below −10 °C. At the January average of −7.9 °C, clear double-glazed windows start to fog at about 53% humidity at the centre of the glass, and at about 37% in a cold snap of −22.5 °C; the edges fog sooner.

How many smoke alarms does a house need in New Brunswick?

Regulation 82-20 makes the NFC 2020 a prescribed fire prevention standard, so the NFC rule applies: an alarm between sleeping areas and the rest of the home, battery alarms permitted. 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 New Brunswick?

No provincial requirement to install CO alarms in existing homes was found. NB's Fire Prevention Act and its Fire Prevention and Inspection Regulation 82-20 (consolidated to 2025-05-01) contain no CO alarm provision; Regulation 82-20 incorporates the National Fire Code 2020 and National Building Code 2020 as standards. New Brunswick applies the NBC 2020 to construction, alteration and demolition under the Building Code Administration Act.

How often should I test my well water in New Brunswick?

Bacteria: Twice a year (spring thaw, fall rains). Chemistry: Inorganics at drilling and every 2 years after. Most of Saint John is on municipal water, but the city's large land area includes rural sections.

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 Saint John

Heating and hot water costs in Saint JohnWhat heating, hot water and air conditioning cost at your local prices, and what each heating system would cost instead.Upgrade payback in Saint JohnSavings, rebates and payback for attic, wall and basement insulation, windows, air sealing and thermostat setbacks.Appliance running costs in Saint JohnWhat 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 Saint John Radon testing in Saint JohnCarbon monoxide testing in Saint JohnWell water testing in Saint JohnMould testing in Saint JohnVentilation assessments in Saint John New Brunswick rebates and programs

Sources

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

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