Understanding Blower Door Testing: What ACH50 Means for Your Home

A blower door test measures a home's air infiltration rate in air changes per hour at 50 pascals of pressure (ACH50). A typical older home measures 8-15 ACH50. Energy Star certification requires 5 ACH50 or less in Climate Zones 1-2 and 3 ACH50 or less in Zones 3-8. Passive House standard is 0.6 ACH50. For every 1 ACH50 reduction through air sealing, expect roughly 3-5% reduction in heating energy use. The test costs $150-400 when done standalone, or is often included free as part of a state-subsidized energy assessment.