A blower door test quantifies air leakage in a building. By depressurizing or pressurizing the structure and measuring the airflow needed to maintain that pressure difference, the test reveals the equivalent leakage area (ELA) a measure representing the combined size of all gaps and cracks allowing air infiltration or exfiltration. This measurement, expressed in square inches or square centimeters, helps visualize the cumulative size of air leaks, as if they were a single opening. For example, an ELA of 100 square inches suggests the combined air leaks are equivalent to a hole of that size.
Understanding a structure’s airtightness is critical for energy efficiency, comfort, and durability. Excessive air leakage leads to increased heating and cooling costs, drafts, and potential moisture problems. Historically, building airtightness was not rigorously evaluated. However, with the growing emphasis on energy conservation and sustainable building practices, these assessments have become increasingly important. They provide valuable data for determining the effectiveness of air sealing measures and identifying areas requiring improvement. These measurements provide a quantifiable metric for evaluating building performance, enabling informed decisions about renovations and retrofits.
