Newfoundland and Labrador · rules and data checked October 8, 2026

Home health check for St. John's

In Health Canada's 2012 survey, 4.0% of 100 homes tested in the Eastern Regional Integrated Health Authority region were above the 200 Bq/m³ radon guideline; the 2024 Cross-Canada survey found Roughly 10% of 278 homes that completed testing exceeded 200 Bq/m³ (about 345 kits distributed in November 2024). for St. John's. St. John's's January averages −4.5 °C (ECCC), with about 35 nights a year below −10 °C, when CMHC advises keeping indoor humidity near 30% to stop window condensation. Newfoundland and Labrador has no rule we could confirm for carbon monoxide alarms in existing houses.

Radon, 2012 survey

4.0%

above 200 Bq/m³ (100 homes)

Radon, 2024 survey

—

St. John's

January average

−4.5 °C

35 nights a year below −10 °C

Private wells

Some

in St. John's

Home health check for St. John's

Four quick checks, set up with St. John's's winter temperatures and Newfoundland and Labrador'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 St. John's.

57%highest humidity before the glass fogs at −4.5 °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 −4.5 °C. It is about 12.2 °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%; St. John's averages 35 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
4
Smoke alarms for full coverage (new-home standard)
6
CO alarms recommended
2

We couldn't confirm a Newfoundland and Labrador 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.

St. John's at a glance

Radon surveys covering St. John's
SurveyResult
Health Canada, 2012Eastern Regional Integrated Health Authority, 100 homes, long-term tests4.0% above 200 Bq/m³; 0.0% above 600
Cross-Canada survey, 2024St. John's (NL) - City of St. John's radon test-kit program, winter 2024-25Roughly 10% of 278 homes that completed testing exceeded 200 Bq/m³ (about 345 kits distributed in November 2024).

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 −4.5 °CAt −12.8 °C
Single glazing with a storm windowU 2.956%46%
Double glazing, clear (1970s–1990s)U 2.8657%47%
Double glazing, low-e and argon (2000s)U 1.870%63%
ENERGY STAR (U 1.22 or better)U 1.2279%73%
Triple glazingU 1.476%69%

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 St. John's sees on about 35 nights a year.

Smoke alarms in Newfoundland and Labrador

Fire Protection Services Regulations s. 5: smoke alarms complying with the adopted codes must be installed in new and existing dwelling units, in existing one- and two-family homes (owner-occupied or rented) unless a municipal by-law governs, and in seasonal cottages and homes. The NL Fire and Emergency Services info sheet states: 'Since 2012, working smoke alarms are required in every bedroom of a home or dwelling, and in cottages and cabins too.'

Existing homes must have them: Yes · Every storey: Not confirmed · In each bedroom: Government info sheet says yes · Interconnected: No

Law: Fire Protection Services Regulations, NLR 45/12 (amended by 108/17, 2/19, 23/26), s. 3 and s. 5

Official source ↗

Carbon monoxide alarms in Newfoundland and Labrador

No provincial requirement to install CO alarms in existing homes was found. The Fire Protection Services Regulations (NLR 45/12, amended to 23/26) require smoke alarms in new and existing dwelling units, including existing one- and two-family homes unless a municipal by-law governs, and in seasonal cottages. They contain no CO alarm provision. They adopt the National Building Code except Part 9 as it relates to one- and two-family dwellings, so building rules for new houses are left to municipal by-laws.

No official NL statement was found that explicitly confirms or rules out a CO alarm requirement for existing homes. Left null.

Official source ↗

Well water in St. John's

Most of St. John's is on municipal water, but the city's boundaries include rural fringe areas.

  • Bacteria: No routine bacteria frequency found on the provincial pages, the provincial guide or the Eastern Health page (last updated 2022-04-05). The guide only says to retest 3-4 months after a successful shock chlorination.
  • Chemistry: Every two years ('Your water supply should be tested for chemical quality every two years to ensure it is free of potential contaminants such as arsenic.') (Private labs only ('Chemical testing is not a free service in this province'); prices not published)

Newfoundland and Labrador source 1 ↗ Newfoundland and Labrador source 2 ↗ Newfoundland and Labrador source 3 ↗

Radon help in Newfoundland and Labrador

New homes: Not province-wide for houses. The Fire Protection Services Regulations (NLR 45/12) adopt the NBC "except Part 9 where relative to one and 2 family dwellings", with new editions taking effect 6 months after publication; CBHCC lists the NBC 2025 as enforced from July 12, 2026. Radon measures in new houses therefore depend on municipal building by-laws, which were not verified here. (NBC 2025 Part 9 adds a passive vertical radon stack for dwelling units.)

Test kits: No provincial program found. The City of St. John's offered about 250 free kits to residents (registration opened Nov 26, 2025), following about 345 kits in Nov 2024. Mount Pearl and Paradise have run similar programs, and several NL public libraries lend radon monitors.

Other help: Lungs Matter mitigation aid (up to $1,500) is available to eligible households (NL income cap $77,400).

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

Common questions in St. John's

How common is radon in St. John's?

Health Canada's 2012 survey found 4.0% of 100 homes tested in the Eastern Regional Integrated Health Authority region at or above 200 Bq/m³. The 2024 Cross-Canada survey, which pools tests that households volunteered, reports Roughly 10% of 278 homes that completed testing exceeded 200 Bq/m³ (about 345 kits distributed in November 2024). for St. John's. 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 St. John's?

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). St. John's averages 35 nights a year below −10 °C. At the January average of −4.5 °C, clear double-glazed windows start to fog at about 57% humidity at the centre of the glass, and at about 47% in a cold snap of −12.8 °C; the edges fog sooner.

How many smoke alarms does a house need in Newfoundland and Labrador?

Fire Protection Services Regulations s. 5: smoke alarms complying with the adopted codes must be installed in new and existing dwelling units, in existing one- and two-family homes (owner-occupied or rented) unless a municipal by-law governs, and in seasonal cottages and homes. The NL Fire and Emergency Services info sheet states: 'Since 2012, working smoke alarms are required in every bedroom of a home or dwelling, and in cottages and cabins too.' 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 Newfoundland and Labrador?

No provincial requirement to install CO alarms in existing homes was found. The Fire Protection Services Regulations (NLR 45/12, amended to 23/26) require smoke alarms in new and existing dwelling units, including existing one- and two-family homes unless a municipal by-law governs, and in seasonal cottages. They contain no CO alarm provision. They adopt the National Building Code except Part 9 as it relates to one- and two-family dwellings, so building rules for new houses are left to municipal by-laws.

How often should I test my well water in Newfoundland and Labrador?

Chemistry: Every two years ('Your water supply should be tested for chemical quality every two years to ensure it is free of potential contaminants such as arsenic.'). Bacteria test cost: Free (provincial). Most of St. John's is on municipal water, but the city's boundaries include rural fringe areas.

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 St. John's

Heating and hot water costs in St. John'sWhat heating, hot water and air conditioning cost at your local prices, and what each heating system would cost instead.Upgrade payback in St. John'sSavings, rebates and payback for attic, wall and basement insulation, windows, air sealing and thermostat setbacks.Appliance running costs in St. John'sWhat 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 St. John's Radon testing in St. John'sCarbon monoxide testing in St. John'sWell water testing in St. John'sMould testing in St. John'sVentilation assessments in St. John's Newfoundland and Labrador rebates and programs

Sources

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

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