Newfoundland and Labrador · Energy · checked September 28, 2026

Ventilation and humidity assessments in St. John's

Condensation on windows, musty basements and stuffy bedrooms are ventilation and humidity problems, and they're easy to confuse with insulation problems. A ventilation assessment measures which one you have.

Get matched in St. John's → The ventilation and humidity assessment
A heat recovery ventilator on a basement wall with four insulated ducts running up between the joists

Cost

Part of an evaluation

Houses built since 2001

26%

Tighter houses that usually rely on an HRV or ERV

Houses built before 1961

22%

Older houses usually leak more and have less insulation

Winter design temperature

−12.8°C

Colder days mean more window condensation

How St. John's is built

St. John's's houses by when they were built Ten house shapes, one for each tenth of St. John's's 42,120 houses. Before 1961: 22%, 1961–1990: 42%, 1991–2000: 11%, 2001 or later: 26%. Older houses glow hotter.
  • Before 1961 22%
  • 1961–1990 42%
  • 1991–2000 11%
  • 2001 or later 26%
Each house stands for one in ten of St. John's's 42,120 houses (single-detached, semi-detached, row and duplex), drawn by when it was built. The glow shows the usual pattern: older houses tend to be leakier and less insulated. More snow in the drawing means more heating degree-days: a longer, colder heating season. Sources: Statistics Canada 2021 Census (table 98-10-0233-01), NRCan HOT2000 climate data.

Why St. John's homes get humidity problems

St. John's gets about 4,578 heating degree-days a year, a measure of how much heating its climate needs, and its winter design temperature, the cold day heating systems are sized for, is −12.8°C. Those figures come from the climate data for St-John's International in HOT2000, the home-energy software Natural Resources Canada (NRCan) gives energy advisors. On St. John's's coldest days, window glass and poorly insulated corners get cold enough for condensation at humidity levels that feel normal indoors, so winter humidity needs to stay at the lower end of the comfortable range.

Of St. John's's 42,120 houses (single-detached, semi-detached, row houses and duplexes), 22% were built before 1961 and 64% before 1991, according to the 2021 Census. Newer houses (26% of St. John's's were built since 2001) are tight and usually have an HRV or ERV that needs balancing and cleaning. Older houses that get air-sealed can lose the accidental ventilation they used to rely on.

What the assessment measures

  • Relative humidity in living areas and the basement.
  • Actual airflow from bath and kitchen fans, and whether they vent outside rather than into the attic.
  • How much fresh air the house gets, and whether an HRV or ERV is balanced.

The ventilation and humidity assessment in detail.

Related tests in St. John's

Mold and air quality testing in St. John's · Radon testing in St. John's

Atlantic Canada Maritimes and Newfoundland

What this means in St. John's’s climate

Damp, windy, icy winters and costly oil: switch to heat pumps, seal, test for radon.

Why it matters here: Damp air and heavy rain make moisture the main risk; this checks fans, indoor humidity and signs of mould.

Best timing: Late fall or the spring wet season.

  • Fix moisture before you insulate. Halifax, St. John's, Saint John and Charlottetown get enough wind-driven rain that new walls must have a rainscreen. Stop water getting into walls and basements before adding insulation. Ask: Ask the advisor to check the basement, attic sheathing and walls under windows for damp, and how bath fans vent.

What else homes in St. John's need →

Sources for this climate guide · checked October 26, 2026

NRCan-licensed service organizations serving St. John's

A service organization is a company that Natural Resources Canada (NRCan) licenses to deliver EnerGuide evaluations; its registered energy advisors do the home visit. Advisors assess ventilation and humidity as part of an evaluation and check that exhaust fans actually vent outside. Sizing an HRV or ERV may be extra.

Source: NRCan list of licensed service organizations, checked September 28, 2026. Call to confirm your street is covered and ask about wait times.

Ventilation and humidity assessment in St. John's: common questions

HRV or ERV?

Both bring in fresh air and recover heat. An ERV also transfers some moisture, which helps keep very dry winter air from getting drier; an HRV suits houses that tend to run humid.

Why did condensation appear after we got new windows?

Tighter windows cut accidental air leakage, so humidity builds up. The fix is usually controlled ventilation, not leakier windows.

Is a ventilation assessment part of an EnerGuide evaluation in St. John's?

Advisors assess ventilation and humidity during the evaluation; HRV or ERV sizing may be an extra service.

Ventilation and humidity assessment near St. John's

Ventilation and humidity assessment in Charlottetown797 kmVentilation and humidity assessment in Halifax893 kmVentilation and humidity assessment in Moncton931 kmVentilation and humidity assessment in Saint John1041 kmVentilation and humidity assessment in Fredericton1070 km All 70 cities →

Sources

Checked September 28, 2026. Census figures are for the municipality (Newfoundland and Labrador); climate data is NRCan's HOT2000 station St-John's International (11 km away).

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