What a Blower Door Test Actually Measures?
A calibrated fan is mounted in an exterior doorway with a temporary panel and used to depressurize the building. Air is drawn out, replacement air pulls in through every gap in the envelope, and the fan measures how much airflow it takes to hold a set pressure difference. That airflow is the leakage rate.
The result is reported as ACH50, the number of times the full volume of air inside the building is replaced each hour at 50 pascals of pressure difference. Depending on the project, results may also be reported as normalized leakage area or normalized leakage rate.
The number tells you how leaky the building is. The walkthrough while the fan is running tells you where. Both matter, and only one of them is on the report by default, which is why the diagnostic portion of the visit is worth asking about before you book.
How Much Does a Blower Door Test Cost in Vancouver?
There is no single price, and any company quoting one without asking questions is quoting for a different scope than the one you need. Cost is driven by five things.
- Building size and volume: A laneway house and a 4,000 square foot custom home take different amounts of fan capacity, setup time and walkthrough time.
- Location. Vancouver, North Vancouver and Burnaby are straightforward. Squamish, Whistler, Mission and the Sunshine Coast carry travel time.
- Number of visits: A single test is one price. A mid-construction test, guided sealing, and a retest is a different engagement. Booking the sequence together costs less than booking each visit separately.
- Diagnostics included: A compliance number alone is the base scope. Adding smoke tracer walkthrough and infrared thermal imaging to locate and photograph individual leaks adds time and equipment.
- Reporting requirements: A number for your own use is one thing. A report formatted for energy model input, a building official, or a certification program is another.
The most common mistake is buying the cheapest possible single test at the end of construction. That gets you a number you can no longer do anything about. The version that saves money is a mid-construction test with sealing and a retest, because it is the only scope where the spend actually changes the outcome.
Send your project address, floor area and construction stage and you get a scoped quote rather than a range.
Mid-Construction Blower Door Testing
The mid-construction blower door test is the only point in a build where a failing airtightness number is still cheap to fix. Once drywall goes up, every leakage path you did not find is behind a finished wall.
The window that decides your final number
There is a short stretch of the build where a blower door test is worth far more than at any other time. It opens when the air barrier and all envelope penetrations are complete, and it closes the moment interior finishes start.
Test too early and the air barrier is not continuous yet. You measure a building that does not exist and the result tells you nothing actionable.
Test in the window and every leakage path you find is reachable. A gap at the top plate is a tube of sealant. A poorly detailed window transition is fifteen minutes of tape. Your crew is already on site with the materials in the truck.
Test too late and the same gap sits behind drywall, primer and paint. Fixing it means cutting, patching, repainting and rescheduling trades, or accepting a number that misses your target.
When to book it
The right trigger is a construction milestone, not a calendar date. Book once all of the following are true:
- Exterior sheathing, weather-resistive barrier and roof are complete
- All windows and exterior doors are installed and their air seals are in place
- All roof, wall and floor penetrations are made and sealed, including plumbing vents, electrical, HVAC, dryer and range exhaust and hose bibs
- Interior air barrier detailing at top plates, rim joists, party walls and attic transitions is complete
- Rough-in inspections are done
- Insulation and drywall have not started
On a typical single family or laneway project in the Lower Mainland that is a window of a few days. Coordinate the booking against your framing and mechanical rough-in schedule rather than waiting for the stage to arrive.
Blower door guided air sealing
Where it is included in scope, the sealing happens with the fan still running and an advisor on site. Your crew seals a path, the leakage reading moves, and you both watch it move. This removes the guesswork about which leaks actually mattered, and it is the fastest route to a target. Sealing effort goes to the paths that shift the number rather than the ones that are easiest to reach.
Mid-construction and as-built testing compared
Mid-Construction Test
As-Built Test
Skipping the mid-construction test is a budget decision made at the wrong end of the project. Builders who run both consistently arrive at the final test already knowing what the number will be.
How the Test Runs on Site
Six stages, from measuring the building to handing over the number. On a single family home the whole sequence typically takes two to three hours, and longer when guided sealing and a retest are included.
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01
Building measurement and setup
Heated floor area, volume and envelope surface area are measured or confirmed against the drawings, because these are the denominators of every metric being reported. The calibrated fan is fitted into an exterior doorway with a temporary panel and reference pressure lines are run to the exterior.
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02
Building preparation
Exterior openings are closed, interior doors are opened so the building behaves as one zone, combustion appliances and mechanical ventilation are set to the required state, and dampers or intentional openings covered by the standard are sealed. Preparation follows the applicable procedure rather than site convenience, because inconsistent preparation is what makes one test impossible to compare against the next.
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03
Depressurization and multi-point measurement
The building is depressurized and airflow is measured across a range of pressure differences rather than at a single point. Baseline pressure, wind and temperature are recorded before and after the sequence. Multi-point data produces a defensible leakage curve instead of a single reading a gust of wind could have skewed.
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04
Leak detection with the fan running
With the building held under pressure, we walk the envelope and locate the actual leakage paths using smoke tracers and, where conditions allow, thermal imaging. Every significant leak is photographed and its location recorded, so what you receive is a list of positions rather than a general observation that the building is leaky.
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05
Sealing and retest, where in scope
Guided sealing happens live, and a retest confirms the improvement before the crew moves on. On mid-construction engagements this is normally scheduled with the original visit.
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06
Metrics and reporting
Results are calculated and reported as ACH50, and as normalized leakage area or rate where the project requires it. For projects on an energy modelling pathway, the measured value is entered into HOT2000 so the model reflects the building as it is actually being built rather than the assumption made at permit stage.
How to Prepare for the Test
Send this to whoever will be on site. A prepared building is the difference between a test that runs in two hours and one that gets aborted.
If any item cannot be met on the day, tell us before we mobilize. Some conditions are workable and others invalidate the result.
Leaks We Find Most Often on Lower Mainland Buildings
These are not hypothetical. They are the paths that show up repeatedly on wood-frame construction in this climate.
- Top plate to attic transitions, particularly at interior partition walls
- Rim joist and floor band at each storey
- Recessed light housings and their wiring penetrations
- Window and door rough opening transitions where the membrane detail was interrupted
- Attic hatches and conditioned attic access panels
- Plumbing stack and vent penetrations through the ceiling plane
- Electrical panel penetrations and service entries
- HVAC duct penetrations through the air barrier
- Bathroom and range exhaust duct terminations
- Party wall and garage common wall interfaces
- Cantilevered floor assemblies and bay projections
Most of these are ten minute fixes before drywall and half day fixes after.
Blower Door Testing and BC Energy Step Code
Your airtightness target is not a universal figure. It comes from the compliance pathway and the energy model prepared for your specific project, and it varies with the Step being targeted, the building geometry and the other measures in the model. A compact two-storey home and a sprawling single-storey with the same target can face very different practical difficulty reaching it. Our BC Energy Step Code consulting covers how that target is set and what it takes to hit it.
What matters on site is this: the number in your energy model is an assumption until someone measures it. The mid-construction test is where the assumption gets tested while there is still time to act on the answer.
Projects pursuing a Net Zero home or Passive House design face targets tighter than the code minimum, and on those projects mid-construction testing becomes effectively mandatory in practice whatever the code requires. A tight envelope also changes mechanical sizing, which is why airtightness results feed directly into heat load calculation.
Testing is performed in general accordance with the standard applicable to your project. We confirm which one applies before the visit rather than after.
Blower Door Testing on Existing Homes
If your house is drafty, expensive to heat, or has rooms that never reach temperature, a blower door test turns those symptoms into a measured number and a mapped list of leakage paths. On existing homes the test is usually most valuable as part of an EnerGuide home energy evaluation, where the leakage result is combined with insulation, mechanical and window assessments so improvements can be ranked by what they actually return.
That pathway also matters for funding. Most retrofit incentives require a pre-upgrade evaluation before work starts, so testing first and applying later is the wrong order. Check what applies to your project under rebates and grants before booking any work.
What You Receive?
- Confirmation of the applicable test standard and target before the visit
- Building measurement and volume calculation
- Written preparation checklist issued ahead of the test date
- Calibrated multi-point depressurization test with recorded environmental conditions
- ACH50 result, with normalized leakage area or rate where the project requires it
- Photographed and located list of significant air leakage paths
- Smoke tracer and thermal diagnostics as conditions allow
- Blower door guided air sealing with an advisor on site, where included in scope
- Retest to confirm improvement, where included in scope
- Preliminary metrics entered into HOT2000 for projects on a modelling pathway
- Written report suitable for your file and for coordination with your energy advisor
- Direct coordination with your energy modeller and building official as needed
Who We Test For?
- Custom home builders working to a Step Code target
- Laneway and infill builders in Vancouver and Burnaby
- Small multi-family and townhouse builders under Part 9
- General contractors on major renovations where the envelope is opened up
- Builders pursuing Net Zero, Net Zero Ready, Passive House or ENERGY STAR
- Homeowners acting as their own general contractor on a new build
- Homeowners investigating drafts, heating costs or comfort problems
Commercial and multi-unit buildings above the Part 9 threshold need a different method entirely, with multiple synchronized fans and a whole-building or multizone approach, as described at the top of this page. Where a project also needs its mechanical systems verified against design intent, airtightness results feed into building commissioning, and larger facilities frequently pair testing with a commercial energy audit.
Book a Blower Door Test
For new construction, the best time to call is when your windows are in and your penetrations are being sealed. That gives enough lead time to schedule inside the mid-construction window rather than after it closes. For existing homes, any time works.
Shahin Arvandi
Founder, Monolith Housing Solutions
- Certified Air Tester
- Level II Infrared Thermographer
- Building Science Specialist
Speak directly with Shahin rather than a call centre. Two minutes on the phone usually settles whether you need a single verification test or the full mid-construction sequence with sealing and a retest.
- Project address and floor area
- Construction stage, or existing home
- Target Step or certification, if you have one
- Your framing and drywall schedule
ITC Thermography Credential ID 253468810
Where We Test?
Vancouver, North Vancouver, West Vancouver, Burnaby, Richmond, Surrey, Delta, Langley, Coquitlam, Port Coquitlam, Port Moody, Maple Ridge, Mission, Squamish, Whistler and the Sunshine Coast.
Coastal winter conditions matter more than people expect. High wind produces baseline pressures that can invalidate a marginal test, so we schedule around forecast conditions and record baseline pressure before and after the sequence rather than testing regardless and hoping the number holds.