Ontario · Energy · checked September 28, 2026

Blower door testing in London

A blower door test measures how leaky a house is and shows where the leaks are. In London, with about 3,809 heating degree-days a year, every leak runs up the heating bill for most of the year.

Get matched in London → The blower door test, step by step
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

Cost

Included in an evaluation

Evaluation price

About $500–$700

Licensed organizations

25

Houses built before 1961

25%

How London is built

London's houses by when they were built Ten house shapes, one for each tenth of London's 119,295 houses. Before 1961: 25%, 1961–1990: 41%, 1991–2000: 11%, 2001 or later: 24%. Older houses glow hotter.
  • Before 1961 25%
  • 1961–1990 41%
  • 1991–2000 11%
  • 2001 or later 24%
Each house stands for one in ten of London's 119,295 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. Snowfall scales with heating degree-days. Sources: Statistics Canada 2021 Census (table 98-10-0233-01), NRCan HOT2000 climate data.

Why air leakage matters in London

London gets about 3,809 heating degree-days a year and has a winter design temperature of −18.4°C, according to NRCan's HOT2000 climate data for London. That's right around the middle of the 70 cities we cover.

Of London's 119,295 houses (single-detached, semi-detached, row houses and duplexes), 25% were built before 1961 and 66% before 1991, according to the 2021 Census. Older houses usually test leakier than newer ones, and an EnerGuide report compares your result with homes of the same era, so you can see whether your house is typical or a problem.

After you seal: two checks

  • Combustion safety. In the London area, the main heating energy is natural gas for 61% of households. A tighter house changes how fuel-burning appliances vent, so the spillage check should be repeated after serious air sealing. Combustion safety testing in London
  • Radon. Sealing shifts the pressure balance between the house and the soil. Health Canada's 2012 survey found 1.8% of 109 homes tested in the Middlesex-London Health Unit health region above the guideline. The larger 2024 Cross-Canada survey reports 3.5% (1 in 29) of houses at or above the guideline for the London, ON (London CMA) metro area. Test before and after big air-sealing jobs. Radon testing in London

What it costs in London

A blower door test is part of every EnerGuide evaluation rather than a separate purchase. Typical Ontario prices are about $500–$700 for the initial EnerGuide evaluation and $200–$450 for the follow-up, plus HST where it applies. Windfall Ecology Centre charges $500 + HST for the initial evaluation and $250 + HST for the follow-up, Reep Green Solutions charges $540 and $406 with no HST, and City-backed programs in Ottawa and London quote $500–$700 as typical for the first visit. Only assessments from the seven HRSP-approved organizations qualify for the $600 Home Renovation Savings rebate, and none of the seven publishes a price.

How the test works

  • A calibrated fan is fitted into an exterior door and pulls air out until the house is at 50 pascals, the standard test pressure.
  • The result is air changes per hour at 50 Pa (ACH50): how many times an hour the whole volume of air would leak out and be replaced at that pressure.
  • While the fan runs, you and the advisor walk the house and feel for leaks at the attic hatch, rim joists, pot lights, trim and plumbing and wiring penetrations.
  • A second test after the work shows what changed, and it is what most rebates pay on.

The blower door test in detail.

NRCan-licensed service organizations serving London

A blower door test is part of every EnerGuide evaluation, so any organization below can do one in London. Ask to walk the house with the advisor while the fan runs.

Only assessments from the seven HRSP-approved organizations qualify for the $600 Home Renovation Savings rebate and its assessment-path upgrade rebates; each listing below says whether it's one of them.

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

Programs that include a blower door test in London

Provincial · needs an evaluation Home Renovation Savings — Home Energy Assessment path Up to $10,000 per home for insulation, windows and air sealing, plus $600 back on your assessments — if the follow-up assessment is done by December 31, 2026 Open · deadline Municipal BetterHomes London loan City of London program (FCM Green Municipal Fund-supported) with a free retrofit coach: loans up to $40,000 at a 2.5% fixed rate, terms up to 20 years, repaid through property taxes, with up to 50% of approved costs paid up front. The project must cut energy use by at least 25% (typically a $20,000-$30,000 investment); at least 80% of costs must be energy efficiency. For detached, semi, townhomes, duplexes and triplexes used as a full-time primary residence. Participants usually pay for the initial energy assessment ($500-$700) before financing approval; EnerGuide assessment costs are eligible for financing. Site updated Sept 2026.

Blower door test in London: common questions

Where can I get a blower door test in London?

Book an EnerGuide evaluation with any of the 25 NRCan-licensed organizations serving London; the blower door test is part of every evaluation.

How much does a blower door test cost in London?

It is included in an EnerGuide evaluation. Typical Ontario prices are about $500–$700 for the initial EnerGuide evaluation and $200–$450 for the follow-up, plus HST where it applies. Windfall Ecology Centre charges $500 + HST for the initial evaluation and $250 + HST for the follow-up, Reep Green Solutions charges $540 and $406 with no HST, and City-backed programs in Ottawa and London quote $500–$700 as typical for the first visit. Only assessments from the seven HRSP-approved organizations qualify for the $600 Home Renovation Savings rebate, and none of the seven publishes a price.

What is a good blower door result?

Lower is better. Your EnerGuide report compares your air changes per hour at 50 Pa with homes of the same era, which is more useful than a single target number.

Does air sealing affect radon?

It can. Tightening a house changes the pressure difference with the soil, so test for radon before and after major air sealing.

Blower door test near London

Blower door test in Waterloo79 kmBlower door test in Kitchener81 kmBlower door test in Brantford82 kmBlower door test in Cambridge90 kmBlower door test in Chatham-Kent98 km All 70 cities →

Sources

Checked September 28, 2026. Census figures are for the municipality (Ontario); climate data is NRCan's HOT2000 station London (10 km away).

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