Which Buildings Need Large Building Airtightness Testing
A residential blower door test and a whole-building airtightness test share the same physics and almost nothing else. Once a building has multiple storeys, shafts, a parkade and a mechanical system with its own pressure relationships, nearly every part of the procedure changes.
Residential Blower Door Test
Large Building Airtightness Test
The metric difference is the one that trips up most project teams. ACH50 divides leakage by interior volume, which flatters tall buildings with large volumes and small enclosure areas. Large buildings are normalized by enclosure surface area instead, so the number you report is the airflow crossing each square metre of the building skin at 75 pascals. If a specification hands you a target in L/s per square metre and your consultant reports ACH50, the two numbers are not interchangeable.
How a Large Building Airtightness Test Is Planned and Performed
Our testing scope covers buildings where a single fan in a single doorway cannot hold pressure across the enclosure. In practice that means most of what gets built in the Lower Mainland above three storeys.
- Part 3 buildings of all occupancy types
- Multi-unit residential buildings, condominiums and rental developments
- High-rise and mixed-use towers with commercial podiums
- Office, retail and hospitality buildings
- Institutional buildings including schools, care facilities and civic buildings
- Industrial, warehouse and cold storage buildings with large enclosure volumes
- Existing buildings undergoing retrofit, recommissioning or envelope renewal
We also run suite compartmentalization testing and guarded party-wall testing for multi-family projects, where leakage between adjoining units has to be separated from leakage through the exterior enclosure. Our Kensington Gate project in Langley is a working example: 91 units where a 79-suite apartment building was tested as one connected zone and 12 attached townhouses were each tested individually with guarded fans on the neighbouring units.
How the Test Is Planned and Performed
A large building test is roughly eighty percent planning and twenty percent fan time. The sequence below is how we run a project from first drawing review to issued report.
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01
Confirm the target, the standard and the enclosure boundary
We start from the specification, the energy model and the architectural set. The leakage target, the reference pressure and the test standard are confirmed in writing, then the tested air barrier boundary is defined: which walls, roofs, floors, party walls and internal separations are inside the tested envelope and which are excluded. Enclosure surface area is calculated at this stage, because it is the denominator of the final number and disagreements about it after testing are expensive.
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02
Size the fan capacity and plan the equipment layout
Required airflow is estimated from enclosure area and the target leakage rate, with headroom for a building that turns out leakier than modelled. That estimate determines fan count, fan positions and where remote pressure references go. On the Kensington Gate apartment building we ran six calibrated Retrotec 5000 fans, three at the ground floor entrance and one distributed on each upper floor, controlled through Retrotec FanTestic Pro from a central station.
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03
Issue the building preparation checklist
The site team receives a written preparation list well before the test date: exterior openings, dampers, HVAC shutdown states, elevator and stair isolation, temporary seals permitted under the standard, and which trades need to be off the floor. Most failed or aborted large building tests are preparation failures, not envelope failures.
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04
Choose the pressure strategy: whole building, multizone or guarded
A building is tested as one zone only if pressure distributes consistently through it. Tall buildings, phased occupancy, compartmentalized floors and attached units need something else. Multizone testing under ASTM E3158 handles internal pressure separation. Guarded testing applies fans to adjoining spaces to reduce the differential across shared walls, so what you measure at the target zone is exterior leakage rather than air borrowed from next door.
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05
Run pressurization and depressurization with distributed monitoring
The enclosure is tested under positive pressure, negative pressure or both, depending on the method and the jurisdiction. Baseline pressure, wind and temperature are recorded before and after. Communication between fan stations matters more than people expect: wireless signal does not travel reliably through concrete floors, so on multi-storey concrete structures we run a hardwired CAT5 network with a switch and router so every fan station stays in sync with the control workstation for the full sequence.
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06
Calculate the normalized leakage rate
Measured airflow is normalized against the agreed enclosure area at the applicable reference pressure and reported as NLR75 in L/s per square metre, alongside the raw airflow and the full multi-point data set. Where a project also requires per-unit reporting, individual suite results are calculated separately using each unit's own enclosure area, orientation and number of shared walls.
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07
Diagnose leakage sites where investigation is in scope
If the result misses the target, or if the team wants leakage located regardless, we apply ASTM E1186 diagnostics under sustained pressure. That means infrared thermal imaging at material transitions and penetrations, smoke tracers at suspected paths, and documented photographs of each significant leakage site rather than a general observation that the building is leaky.
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08
Report and coordinate
The report documents boundary, equipment configuration, environmental conditions, raw and normalized data, the comparison against target, and any diagnostic findings. We then coordinate directly with your energy modeller, building envelope consultant and the responsible professionals so the number lands in the compliance submission in the format the AHJ expects.
Standards and Protocols We Test To
Airtightness standards fall into two groups that are often confused. One group measures how much air leaks. The other locates where it leaks. A compliance submission needs the first. A remediation plan needs both.
These produce the measured leakage rate your compliance submission is built on.
ASTM E779
Fan pressurization method for determining enclosure air leakage rate. The most commonly referenced standard for BC Part 3 compliance where the building behaves as one pressure zone.
ASTM E3158
Developed specifically for large and multizone buildings. Applies where size, geometry or internal pressure separation makes single-zone testing unreliable.
ASTM E1827
Orifice blower door method, used where equipment configuration or building conditions make it the more appropriate procedure.
CAN/CGSB-149.10
Canadian fan depressurization method, referenced in some specifications and incentive programs.
ANSI/RESNET/ICC 380
Enclosure airtightness testing standard, referenced in ENERGY STAR Multifamily and several incentive pathways.
These locate leakage paths. They do not produce a pass or fail number.
ASTM E1186
Leakage site detection using infrared thermography, smoke tracers and pressure diagnostics. Tells you where air is moving, not how much.
These sit on top of a quantitative method and govern how the work is planned, prepared and reported.
USACE Air Leakage Test Protocol v3
Detailed planning, preparation, data collection and reporting procedure layered on top of fan pressurization testing.
ABAA Standard Method
Building enclosure airtightness compliance testing method from the Air Barrier Association of America, referenced in some project specifications.
The standard is not a preference. It is written into your project specification, your energy model assumptions, or the requirements of the Authority Having Jurisdiction, and it needs to be confirmed before the test plan is drafted rather than after the fans arrive.
Large Building Airtightness Testing Requirements in Vancouver and the Lower Mainland
Requirements differ between the City of Vancouver and the rest of the province, and that catches out teams working across municipal boundaries.
The City of Vancouver operates under the Vancouver Building By-law and publishes its own testing expectations in Building Bulletin 2023-004, which addresses test method, enclosure area calculation, pressurization and depressurization, and how results are coordinated with the energy model. Everywhere else in the Lower Mainland, Part 3 projects follow the BC Energy Step Code and the applicable Part 3 compliance pathway, with NECB referenced under certain pathways.
Two local factors shape how we plan a test here:
- Wind and stack effect. Coastal winter conditions in North Vancouver, West Vancouver, Squamish and Whistler produce baseline pressures that can invalidate a marginal test. We schedule around forecast wind and record baseline conditions before and after the test sequence.
- Podium and parkade construction. The typical Lower Mainland form of a wood-frame or concrete residential block over a shared underground parkade means the parkade is almost always excluded from the tested volume, and the connection points, stairs, elevator shafts and vestibules, have to be isolated deliberately.
We test across Vancouver, North Vancouver, West Vancouver, Burnaby, Richmond, Surrey, Delta, Langley, the Tri-Cities, Maple Ridge, Mission, Squamish and Whistler, including active development areas such as the Cambie Corridor, River District, Mount Pleasant, Brentwood, Metrotown, Willoughby Heights and Central Surrey.
What You Receive
Deliverables are set in the proposal and scale with the project. A typical Part 3 engagement includes the following.
- Review of project airtightness requirements, specification and target
- Architectural and building envelope drawing review
- Enclosure area calculation and test boundary documentation
- Fan capacity analysis and equipment layout plan
- Written building preparation checklist issued to the site team
- Whole-building, multizone, compartmentalization or guarded testing strategy
- Calibrated pressurization and depressurization testing per the applicable standard
- Recorded airflow, pressure, wind and temperature data across all test points
- Normalized air leakage calculation reported as NLR75 in L/s per square metre
- Per-unit results where suite-level reporting is required
- Comparison against the project target with pass or shortfall stated plainly
- Photographic documentation of the test setup and boundary conditions
- ASTM E1186 smoke tracer and infrared diagnostics where included in scope
- Documented list of significant leakage locations with photographs
- Final airtightness test report formatted for AHJ submission
- Data package prepared for the energy modeller
- Retesting after corrective work, where requested
Where a signed or sealed report is required, the reporting responsibility and the professional involvement are confirmed in writing before testing begins.
When to Bring the Testing Provider In
The single most common source of trouble on Part 3 airtightness is late engagement. By the time a building is finished, every decision that affects the result has already been made.
Project stage | What can still be influenced |
|---|---|
Design and specification | Target selection, test standard, boundary strategy, testability of the enclosure design |
Air barrier installation | Detailing at transitions, penetrations and interfaces, before they are covered |
Mid-construction | Optional interim test to find defects while they are still cheap to fix |
Substantial completion | Preparation quality and scheduling only |
Post-completion | Remediation cost and re-test scheduling |
A mid-construction test is not required by code, but on a large building it is usually the difference between sealing an exposed transition detail and opening finished assemblies to reach it.
Large Building Airtightness Testing vs Residential Blower Door Testing
Air leakage shows up in the energy model first, but it rarely stops there. On a large building the enclosure and the mechanical system are one connected pressure problem.
- Energy model accuracy: The modelled leakage assumption feeds the heating and cooling loads. If the tested value comes in significantly above the assumption, the model no longer describes the building, and the compliance path built on it becomes questionable.
- Mechanical system behaviour: Excessive enclosure leakage interferes with corridor pressurization, suite ventilation, exhaust performance and the pressure relationships the designer intended. Systems that were correctly specified can still underperform in a leaky enclosure, which is why airtightness results are useful input to building commissioning.
- Moisture risk: Air carries far more moisture into assemblies than vapour diffusion does. Leakage paths at curtain wall interfaces, floor line transitions and service penetrations are the same paths that carry warm interior air into cold assemblies in a coastal winter.
- Occupant complaints: Drafts, cold corner suites, corridor door pressure and noise transfer between units frequently trace back to enclosure and party wall leakage that a compartmentalization test would have identified.
If your project is a Part 9 house, laneway home or small townhouse, a single calibrated fan is the correct tool and our blower door test service covers it. The comparison below explains why the two procedures share their physics and almost nothing else.
Talk to a Certified Air Tester About Your Project
Every large building test is a different problem, and the useful conversation happens before a proposal is written.
Shahin Arvandi
Founder, Monolith Housing Solutions
- Certified Air Tester
- Level II Infrared Thermographer
- Building Science Specialist
Speak directly with Shahin about your building type, your leakage target, your construction schedule and whether a whole-building, multizone or guarded approach fits your enclosure. Send your architectural drawings and the airtightness section of your specification, and you get a scoped proposal rather than a generic quote.
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
- Sunshine Coast
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