Blower Door Test in Langley, BC: The Kensingtown Multi-Family Project
Project Snapshot
- Project: Kensington Gate, a 91-unit development by Quadra Homes, comprising a 79-unit apartment building and 12 three-storey townhouses across four separate buildings
- Location: 20932 & 20958 83rd Avenue, Willoughby Heights (Yorkson), Langley Township, BC
- General Contractor: Black Maple Construction
- Service: Large building airtightness testing, party-wall guarded testing, and air tightness compliance reporting
- Performed by: Monolith Housing Solutions
- Goal: Verify airtightness performance across two structurally different building types on the same site, and give the builder accurate data for both the shared apartment envelope and each individual townhouse.
Why This Project Needed Two Different Testing Approaches
Most multi-family projects fall into one category: either a single large building tested as one zone, or a row of townhouses tested unit by unit. Kensington Gate needed both on the same site. The 79-unit apartment building sits above a shared underground parkade and had to be evaluated as a single connected envelope, while the 12 townhouses across four separate buildings each needed to be tested and reported on individually, with special attention paid to the shared walls between attached units. Our large building airtightness test service is built around exactly this kind of split scope, where the testing strategy has to match the building type rather than the other way around.
Apartment Building: Whole-Building Multi-Fan Testing
The apartment component was tested as one connected envelope. The three sub-steps below cover how the boundary was set, why six fans were used, and how they were kept in sync.
1
Defining the Test Boundary
The apartment component is a four-storey building with 79 residential suites connected by conditioned corridors, served by dedicated heat-recovery ventilation, electric baseboard heating, and provisions for portable air conditioning. Before any fan was switched on, our team reviewed the architectural drawings, calculated the conditioned volume and enclosure area, and set the test boundary. The underground parkade was isolated from the conditioned space entirely, the elevator shaft was sealed off and excluded from the tested volume, and the stair connection to the parkade was closed with a temporary isolation barrier. Interior doors stayed open so the suites, corridors, and amenity spaces behaved as one pressure zone, matching the as-operated condition described on our mid-construction blower door test page.
2
Six Fans, One Building
A single blower door is enough for a house. A four-storey building above a parkade is a different problem. To move enough air and hold pressure evenly across the full height and length of the structure, we deployed six calibrated Retrotec 5000 blower door fans at once: three at the main ground-floor entrance and one distributed fan on each upper floor. Differential-pressure checks confirmed the building was responding as one interconnected zone rather than several loosely connected sections.
3
Coordinating Six Fans Without Losing the Building
Running six fans in sync is a control problem as much as an airflow problem. The full setup was managed through Retrotec FanTestic Pro, with one digital manometer acting as the primary pressure-control gauge and the remaining fan and gauge assemblies following synchronized speed commands, while each fan kept measuring its own airflow independently. Wireless signal doesn’t travel reliably through concrete floors and multiple storeys, so instead of guessing, we wired the entire building with a dedicated CAT5 network, a switch, and a router, giving every fan station stable communication with the central workstation for the full pressurization and depressurization sequence, in general accordance with ASTM E779.
Apartment Building: Equipment and Crew
The apartment test relied on a coordinated multi-fan setup and a dedicated crew spread across every floor. The full equipment and staffing breakdown is below.
| Category | Details |
|---|---|
| Fans | Six calibrated Retrotec 5000 blower door fans |
| Pressure instrumentation | Retrotec DM32 and DM32X digital manometers, plus independent differential-pressure instruments |
| Control software | Retrotec FanTestic Pro |
| Network | CAT5 cabling, network switch, router (wired due to unreliable wireless across the concrete structure) |
| Other equipment | Fan frames and installation panels, pressure tubing and exterior reference lines, temporary sealing and boundary materials |
| Crew | Lead test operator, central FanTestic control personnel, distributed fan-station technicians per floor, pressure-monitoring staff, and boundary/communication field personnel |
Townhouses: Individual and Guarded Testing
The townhouses were the opposite problem: many small zones instead of one large one. The steps below cover per-unit setup, why guarded testing was needed, and how it was run.
Twelve Units, Four Buildings, Twelve Test Zones
Unlike the apartment building, the 12 townhouses could not be treated as one zone. They’re split across four buildings, two with four side-by-side units and two with two side-by-side units, and each unit has its own lower level with direct access to the shared underground parkade, a dedicated HRV, a ductless mini-split heat pump, and supplemental electric baseboard heating. We calculated conditioned floor area, enclosure area, and volume separately for every single unit based on its location, orientation, and number of shared walls, then tested each one following the EnerGuide Rating System technical procedure, with exterior doors and windows closed and latched and the HRV turned off.
When a Standard Test Isn’t Enough: Guarded Testing
For a detached house, a single-fan test tells you what you need to know. For a townhouse sharing a wall with the unit next door, it doesn’t, because air can leak sideways through the party wall instead of out through the exterior envelope, and a standard test can’t tell the two apart. On several interior units at Kensington Gate, the initial single-fan test showed exactly this: substantial airflow across the shared party-wall assemblies. To isolate the real number, we ran guarded airtightness tests: one blower door fan tested the target townhouse while additional fans depressurized the adjoining units to roughly the same pressure, reducing the differential pressure across the shared walls so the airflow measured at the target unit reflected the exterior enclosure, not leakage borrowed from the neighbours.
Coordinating a Guarded Test in Real Time
Guarded testing only works if every unit involved stays in sync throughout the test. The target-unit test was run through Retrotec’s rCloud platform, with two trained technicians manually controlling the neighbouring-unit fans while the target-unit operator monitored the automated multi-point sequence, adjusting continuously to keep matching pressures across all participating units for the full test duration.
Townhouses: Equipment and Crew
Standard unit testing needed a single technician, while guarded testing required a coordinated three-person crew. The equipment and staffing are listed below.
Category | Details |
|---|---|
Fans | Calibrated Retrotec blower door fans (individual frames and panels) |
Pressure instrumentation | Retrotec DM32 and DM32X digital manometers, plus independent manometers for party-wall pressure monitoring |
Control software | Retrotec rCloud |
Other equipment | Pressure tubing and exterior reference lines, communication equipment for guarded-test coordination |
Crew | One qualified blower door technician for standard unit testing; a three-person field crew (one target-unit operator plus two adjacent-unit technicians) for guarded testing |
Technical Data and Reported Results
Because the apartment building and the townhouses have fundamentally different enclosure geometries, the metrics were calculated and reported separately for each:
- CFM50 (Cubic Feet per Minute at 50 Pascals): total measured air leakage for the apartment building as a single zone, and separately for each individual townhouse.
- ACH50 (Air Changes per Hour at 50 Pascals): the core compliance metric under the BC Energy Step Code, reported per building for the apartment component and per unit for the townhouses.
- Normalized leakage per unit area: used to compare envelope tightness across all 91 units on a fair, like-for-like basis, and to separate true exterior enclosure leakage from party-wall transfer on the guarded townhouse tests.
Engineering Recommendations
With both data sets in hand, the Monolith engineering team provided targeted recommendations for each building type:
- For the apartment building: sealing weak points identified along the shared corridors, elevator shaft boundary, and stair connection to the parkade.
- For the townhouses: sealing and reinforcing insulation at the exterior envelope points identified during guarded testing, separate from the party-wall areas.
- Across both: repairing and sealing air distribution ductwork tied to the HRV systems.
What This Means for the Owner and Builder
Testing 91 units across two building types in one engagement gave Black Maple Construction a single, coordinated roadmap instead of two disconnected reports. With the recommended corrections in place, the development gains:
- Lower operating costs across both the apartment suites and the townhouses, which connects directly to real blower door test energy savings.
- Better thermal comfort, with fewer cold drafts in both the corridor-connected suites and the individually tested townhouses.
- Improved air quality, keeping outdoor moisture, dust, and pollutants out of every unit type on the site.
For projects aiming at the highest performance tier, this same combination of whole-building and guarded testing supports the path toward net zero homes.
Need an Air Tightness Compliance Report?
If you are building or renovating in Langley or anywhere across the Lower Mainland and need an accurate assessment of your building’s energy performance, Monolith Housing Solutions is ready to help. Explore our full range of energy audit services, or browse more of our projects.
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A look at the blower door test on the Kensingtown project in Langley, from equipment setup to live depressurization and leakage measurement across all twelve units.
