Commercial blower door testing is a diagnostic method used to measure and verify the airtightness of a building’s envelope. Using high-capacity calibrated fans installed in exterior openings (typically doors), the building is pressurized or depressurized to quantify air leakage. This testing is required for many projects to comply with the International Energy Conservation Code (IECC) and local energy codes.

During the test, technicians measure airflow (CFM) at a specific pressure differential (commonly 75 Pascals for commercial buildings). The results are then converted into metrics such as CFM per square foot of envelope area, which determines whether the building meets code requirements. Large commercial structures may use multiple synchronized fans to accurately test the entire envelope.

Beyond compliance, blower door testing helps identify leakage paths around penetrations, joints, curtain walls, roof-to-wall transitions, and mechanical openings. When combined with infrared thermography or smoke testing, it provides a clear visualization of problem areas, allowing contractors to correct deficiencies before final inspection.

The result is a tighter, more energy-efficient building that reduces HVAC load, improves occupant comfort, and ensures long-term performance.