A blower door machine is a calibrated fan system that measures air leakage rates in buildings by creating controlled pressure differences between indoor and outdoor spaces. It quantifies infiltration and exfiltration, typically expressed in air changes per hour (ACH) at 50 Pascals (ACH50). This diagnostic tool helps HVAC professionals identify energy losses and comfort issues caused by unsealed gaps, cracks, or poorly installed ductwork.
Technical Specifications
The device attaches to a doorway frame and uses a variable-speed fan to depressurize or pressurize a building. Standard testing occurs at 50 Pa differential pressure, which accelerates natural leakage patterns for measurable results. Results are reported as CFM50 (cubic feet per minute at 50 Pa) or converted to ACH50 for comparison against building codes and energy standards like IECC or ASHRAE 62.2.
Practical Applications
Blower door testing identifies ductwork leakage, infiltration through walls and foundations, and effectiveness of air sealing work. HVAC contractors use results to prioritize weatherization improvements and verify system performance after retrofits. Energy auditors rely on this tool to assess whole-building envelope tightness before recommending efficiency upgrades.