Ontario · 16 local services · checked September 28, 2026

Home energy audits and home testing in Thunder Bay

Thunder Bay gets about 5,405 heating degree-days a year (cold winters: heating dominates), 43% of its houses were built before 1961, and 8 NRCan-licensed service organizations list its postal codes. Pick a service for the local details.

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A Victorian red-brick semi-detached house with a front porch in autumn

How Thunder Bay is built

Thunder Bay's houses by when they were built Ten house shapes, one for each tenth of Thunder Bay's 37,935 houses. Before 1961: 43%, 1961–1990: 41%, 1991–2000: 7%, 2001 or later: 9%. Older houses glow hotter.
  • Before 1961 43%
  • 1961–1990 41%
  • 1991–2000 7%
  • 2001 or later 9%
Each house stands for one in ten of Thunder Bay's 37,935 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.

Thunder Bay at a glance

Climate

Thunder Bay gets about 5,405 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 −28.6°C. Those figures come from the climate data for Thunder Bay in HOT2000, the home-energy software Natural Resources Canada (NRCan) gives energy advisors. Cold winters: heating is the biggest energy cost, so stopping leaks and insulating come first.

Housing

Of Thunder Bay's 37,935 houses (single-detached, semi-detached, row houses and duplexes), 43% were built before 1961 and 84% before 1991, according to the 2021 Census. The typical house dates from 1961–1970.

Heating

In the Thunder Bay area, 84% of households heat mainly with a forced-air furnace; natural gas is the main heating energy for 81% of households (Statistics Canada, 2023).

Radon

Health Canada's 2012 survey found 12% of 108 homes tested in the Thunder Bay District Health Unit health region above the guideline. The larger 2024 Cross-Canada survey reports 34.3% (1 in 3) of houses at or above the guideline for the Thunder Bay, ON (Thunder Bay CMA) metro area.

Very Cold East Northern Ontario, Saguenay, Quebec City

What homes in Thunder Bay need

Deep, snowy winters: stop ice dams, and pair a cold-climate heat pump with backup heat.

Winters here are long and deep, with cold snaps of −25°C to −31°C and the heaviest snow loads of any region we cover. Heat escaping into the attic melts roof snow from below, which refreezes as ice dams. An EnerGuide evaluation here should focus on the attic, the basement and rim joists, and a heating plan with reliable backup heat.

In Thunder Bay: Thunder Bay ranked among Canada's highest-radon municipalities in the 2024 national survey, so test every home. Winters bring cold snaps near −31°C and heavy snow loads, so seal the attic and keep the gas furnace as backup to any heat pump.

What drives bills and comfort here

  • Long, deep heating season: cold snaps reach −25°C to −31°C.
  • Snow lies 10 cm or deeper on the ground for 99 to 134 days a year, so attic heat leaks readily form ice dams.
  • Electric heat serves 76% to 78% of homes around Saguenay and Quebec City; gas heats 74% in Sudbury and 81% in Thunder Bay.
  • Summers are mild but can be humid, with about 23 to 31 days a year at a humidex of 30 or more.

Local risks to plan for

  • About 28 days a year with wind chill below −30.
  • Heavy snow loads; attics that leak heat are prone to ice dams.
  • Radon: the 2024 survey listed Thunder Bay among Canada's 18 highest municipalities.

What to check first, and why

  1. Stop ice dams at the attic

    NRCan says the best way to prevent ice dams is sealing attic air leaks and insulating thoroughly, so roof snow stays frozen. Snow loads here are the heaviest of any region we cover.

    Ask your energy advisor: Ask the advisor to trace attic bypasses with the blower door and thermal camera, and to check insulation depth.

    Attic inspectionBlower door testInfrared (thermal) scan

  2. Cold-climate heat pump with reliable backup

    Cold snaps of −25°C to −31°C are at or beyond many heat pumps' limits, so backup heat is a must: baseboards in most Quebec homes, the furnace in Ontario.

    Ask your energy advisor: Ask for a heat-loss calculation and a heat pump with published capacity near −25°C to −30°C.

    Heat-loss calculation

  3. Insulate the basement and rim joists

    Basements can be about 20% of a home's heat loss, and the long cold season makes the savings add up. Rim joists are often among the leakiest spots.

    Ask your energy advisor: Ask whether the basement is dry enough to insulate from inside, and how much the rim joist leaks.

    Infrared (thermal) scanBlower door test

  4. Test for radon

    Thunder Bay ranked among the highest municipalities in the 2024 national survey, and about 1 in 6 Quebec homes tested at or above Health Canada's guideline.

    Ask your energy advisor: Run a 3-month test in the heating season, and retest after air sealing.

    Radon test

  5. Ventilate and keep humidity in check

    Winter air is very dry, but humidifying too much frosts windows and wets the attic. Balanced ventilation keeps a tighter house fresh without adding moisture problems.

    Ask your energy advisor: Ask for a ventilation assessment and the indoor relative humidity your windows can handle in deep cold.

    Ventilation assessment

Tests that matter most here

  • Blower door test Finds the attic and rim joist leaks that feed ice dams. Best timing: Any season; most useful with a thermal scan in winter.
  • Infrared (thermal) scan Shows missing insulation and air leaks clearly in the cold. Best timing: November to March, on calm days with little sun on the walls being scanned.
  • Attic inspection Frost, wet sheathing and roof melt patterns show where heat escapes; watch where snow melts first after a light snowfall. Best timing: Early winter, after the first light snow or a heavy frost.
  • Radon test Regional radon risk, and air sealing can change indoor levels. Best timing: At least 91 days in the heating season.
  • Combustion safety test In gas-heated Ontario homes, tightening can make appliances spill exhaust. Best timing: During the blower door visit.

Upgrades that usually pay off here

  1. Attic air sealing and insulation to R-59. Today's new-home attic minimum here is about R-59. Sealing first, then insulating, is the best way to prevent ice dams. Have old vermiculite insulation tested for asbestos before disturbing it.
  2. Cold-climate heat pump, keeping your backup. Cold-climate units work to about −30°C and use much less electricity than baseboards; keep baseboards or the furnace for the coldest nights.
  3. Basement and rim joist insulation. A large heat-loss area over a long season. Fix any dampness before insulating from inside.
  4. HRV or ERV for balanced ventilation. Controls humidity and air quality once the house is tighter.

Heating and cooling equipment

  • Choose a cold-climate heat pump with published capacity near −25°C to −30°C, and keep full backup heat for colder nights.
  • Set electric backup 2–3°C below the heat pump's setting so the heat pump does most of the work.
  • Look for demand-defrost controls, which are generally more efficient; ground-source heat pumps need no defrost at all.
  • Cooling needs are modest, but humid spells make a heat pump's cooling a welcome bonus.

Health and comfort

  • Radon: about 1 in 8 Ontario homes and 1 in 6 Quebec homes tested at or above 200 Bq/m³ in the 2024 survey. Test every home.
  • Dry indoor air in deep cold: keep relative humidity within what your windows can handle without frosting.
  • Carbon monoxide: put CO alarms near every fuel-burning appliance and outside sleeping areas.
  • Heavy summer rain happens too: Quebec City had its wettest July in 150 years in 2023, so check basement drainage.

Common mistakes in this climate

  • Chopping ice dams with an axe or pick. It damages the roof. Fix the attic air leaks and insulation that cause them.
  • Heat pumps without backup heat. Cold snaps here go beyond many units' cut-off. Keep baseboards or the furnace.
  • Over-humidifying in winter. It frosts windows and can wet attic sheathing.
  • Skipping the radon retest after tightening. Air sealing can change radon levels; retest in the next heating season.

When to book: Book the evaluation from November to March for clear thermal scans, and check the attic after the first light snow. Start a 3-month radon test in the heating season.

Sources for this climate guide · checked October 26, 2026

Local service guides for Thunder Bay

Energy audits and tests

An energy advisor’s kit on a front-hall bench: infrared camera, pressure gauge with tubing, tape measure, headlamp and a floor sketch

Home energy audit

8 licensed organizations Companies NRCan licenses to do EnerGuide evaluations
A red blower-door panel with a large fan fitted into the front doorway of a brick bungalow, a pressure gauge on a stool inside

Blower door test

5,405 degree-days Cold winters: heating dominates
Hands holding an infrared camera aimed at a ceiling corner beside a frosty window; the screen shows a cold streak

Thermal imaging inspection

5,405 degree-days Cold winters: heating dominates
A kitchen table with a house floor plan, a laser measure, a tape measure and a laptop showing the plan

Heat loss calculation

Design temp −28.6°C The cold day heating is sized for
A duct-testing fan on a basement floor connected by flexible duct to a furnace, a pressure gauge hanging from a joist

Duct leakage testing

84% forced-air Share of homes with ducts that can leak
A gloved hand inserting a combustion analyzer probe into a furnace flue pipe in a basement

Combustion safety test

81% heat with gas Gas appliances need a venting check
A heat recovery ventilator on a basement wall with four insulated ducts running up between the joists

Ventilation and humidity assessment

9% built since 2001 Newer, tighter homes rely on fans or an HRV
Loose-fill insulation between attic joists, a yellow ruler showing its depth and frost on the roofing nails above

Attic insulation inspection

84% built before 1991 Older attics usually need more insulation
Utility bills and a phone showing a monthly energy-use chart on a kitchen table

Energy bill analysis

Synergy North Download 12 months of usage from your account

Home health tests

A small digital radon monitor on a bookshelf in a finished basement family room

Radon testing

34.3% at or above guideline (2024) Neighbours' results don't predict yours: test
A carbon monoxide alarm on an upstairs hallway wall outside the bedrooms at night

Carbon monoxide testing

Required by law
A moisture meter pressed into water-stained basement drywall, an air-sampling pump on a tripod nearby

Mould and indoor air quality testing

84% built before 1991 Older homes have more damp spots
A gloved hand holding a sealed sample bag above vermiculite insulation between attic joists

Asbestos and vermiculite testing

84% built before 1991 Common in materials until about 1990
A gloved hand swabbing layers of cracked old paint on a wooden window sill

Lead paint testing

43% built before 1961 Pre-1960 paint probably contains lead
Filling a water-sample bottle at a farmhouse kitchen tap with the aerator removed, snowy fields and a barn outside

Well water testing

Wells in some areas Only homes on private wells need it

For businesses and buildings

An auditor walking between rooftop heating and cooling units on a snowy commercial roof

Commercial energy audit

5 incentive programs

Who does energy evaluations in Thunder Bay

8 NRCan-licensed service organizations list Thunder Bay postal codes. See the list with phone numbers and coverage →

Rebates and financing for Thunder Bay homes

Provincial · needs an evaluation Home Renovation Savings — Home Energy Assessment path Up to $10,000 per home ($5,000 if heated with Enbridge gas), including $600 back on your two assessments, for insulation, windows, air sealing and more — if the follow-up assessment is done by December 31, 2026 Open · deadline Provincial Home Renovation Savings — direct rebates (no assessment) Heat pumps up to $7,500 ($12,000 ground-source), solar with battery up to $10,000, plus attic, thermostat and appliance rebates — no assessment needed Open Federal National Heat Pump Rebate Announced October 8, 2026 and opening early 2027: up to $10,000 below the median income, $2,000 for other eligible homeowners Announced · opens 2027 Federal CMHC Eco Improvement premium refund A 25% energy-efficiency rebate on your CMHC mortgage insurance premium after $20,000 of energy renovations Open

Cities near Thunder Bay

Winnipeg590 kmGreater Sudbury665 kmWindsor846 kmChatham-Kent864 kmBarrie869 kmWaterloo875 km All 70 cities →

Sources

Checked September 28, 2026.

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