Large Building
Airtightness Testing
Professional whole-building airtightness testing for mid-rise, commercial, and multi-unit residential projects across BC. ASTM E779-compliant testing with experienced Energy Advisors.
Airtightness Testing for Part 3 Projects
Large building airtightness testing measures how much air moves through a building's envelope under controlled pressure conditions. For Part 3 buildings this is a fundamentally different undertaking than single-family blower door testing.
Where a Part 9 residential test most often requires minimal preparation (relatively speaking) and a single blower door fan, large building testing requires multiple coordinated blower door fans running simultaneously to pressurize or depressurize the full building envelope. Results are reported in accordance with ASTM E779 and are used to verify the airtightness assumptions in the energy model submitted for BC Energy Step Code compliance.
As registered Energy Advisors, Thrive Energy provides the in-field measurement data that sits alongside the engineer's energy model - confirming that the building enclosure performs as designed before occupancy.
Is This Service Right for Your Project?
Large building airtightness testing applies to a range of project types. If your project falls under Part 3 of the BC Building Code and is targeting BC Energy Step Code compliance, you likely need this service.
Multi-Unit Residential
Multi-unit residential buildings over 3 storeys - including purpose-built rental, strata, and mixed-use with residential above grade - where whole-building airtightness verification is required for Step Code compliance.
Builders & Developers
Project teams working with a Professional Engineer on Part 3 compliance documentation who need a certified third party to perform and report on the in-field airtightness test.
Architects & Engineers
Design and engineering teams who need a reliable airtightness testing partner to collect the field data that validates their energy model assumptions and completes the compliance package.
What to Expect
Part 3 Large building testing requires more coordination and preparation than Part 9 residential testing. Here is what the process looks like from start to finish.
Send Us Your Architectural Drawings
Share your architectural drawings and project details. We'll review building volume, exterior envelope area, number of units, and project schedule to scope the work accurately. Because every large building is different, pricing is project-specific - there's no standard rate list.
Pre-Test Coordination
We work with your team to confirm the building is ready for testing. This includes verifying that HVAC intake and exhaust grilles, relief dampers, and mechanical penetrations have been temporarily sealed. Proper preparation prevents failed tests and costly re-mobilizations.
On-Site Testing
After proper site-preparation is confirmed, multiple calibrated blower door fans are installed at exterior openings and run simultaneously. We complete both depressurization and pressurization tests. For high-rise configurations, guarded floor-by-floor testing is used to obtain accurate zone-level results. Environmental conditions, wind speed, temperature, and stack effect, are monitored throughout.
Results & Reporting
Results are reported in Air Changes per Hour (ACH) and Normalized Air Leakage Rate (NLR). We provide a clear summary document that your engineering team can reference in the Step Code compliance package submitted to the Authority Having Jurisdiction.
How Large Building Testing Differs from Residential
If you've worked with Thrive Energy on Part 9 residential projects, it's worth understanding how this scope differs, both technically and logistically.
Multiple Fans, One Test
Residential testing most often uses a single blower door fan. Large building testing requires multiple coordinated fans running simultaneously to create and maintain the required pressure differential across the entire building envelope.
Engineer & Advisor Roles Are Separate
For Part 3, the energy model is prepared by a Professional Engineer (there are a few exceptions to this). Thrive Energy provides the independent airtightness measurement. The two deliverables complement each other in the final compliance submission.
More Preparation Required
The building must be properly prepared before testing begins. Mechanical openings need to be sealed, the building must be enclosed, and scheduling must account for weather conditions. Coordination starts well before the test date.
Weather & Conditions Matter More
Stack effect, wind speed, and temperature differentials have a greater influence on results in large buildings. Testing is scheduled during low-wind periods. If conditions deteriorate, we may need to reschedule to protect result integrity.
Different Metrics
Residential testing reports ACH50. Large building results are typically reported as Normalized Leakage Rate (NLR) in L/s·m² at 75 Pa, which accounts for the building's volume-to-surface-area ratio.
Project-Specific Pricing
Large building testing is scoped individually based on building size, configuration, number of fans required, and site conditions. There's no standard rate. Contact us with your architectural drawings for a job-specific estimate.
Where Airtightness Testing Fits in Step Code Compliance
As Part 3 Energy Step Code requirements roll out across BC municipalities, airtightness testing is now a standard compliance requirement for mid-rise and commercial construction, not just high-performance or net-zero projects.
- Airtightness testing validates the enclosure performance assumed in the engineer's energy model
- Test results are documented in the final compliance checklist submitted to the Authority Having Jurisdiction
- Achieving results that align with modelled targets confirms the building performs as designed
- Testing is a construction and occupancy-stage verification - it happens in the field, not on paper
- Energy Advisors are well-positioned to provide this testing, often more cost-effectively than engineering firms
Every Project Gets a Project-Specific Estimate
Large building airtightness testing is scoped based on your specific project — building size, configuration, height, number of fans required, and location all factor into the cost. Send us your architectural drawings and we'll come back to you with a clear, itemized estimate with no surprises.
Send Your Drawings for a Quote