A blower door test uses a powerful calibrated fan, temporarily mounted in an exterior doorway, to depressurize a home, drawing air in through every gap and crack in the building envelope, allowing energy auditors to measure the home’s total air leakage rate and identify specific leak locations.
This depressurization exaggerates the effect of air leaks, making them easier to detect through smoke pencils, infrared cameras, or simply feeling for drafts at suspected leak locations that might not be noticeable during normal, non-depressurized conditions.
The test produces a quantifiable measurement of the home’s total air leakage, expressed in units like air changes per hour, giving auditors and builders an objective number to compare against code requirements or track improvement after air sealing work is completed.
What Does a Blower Door Test Involve?
- A calibrated fan mounted in an exterior doorway
- Depressurizing the home to exaggerate air leaks
- Measurement of total air leakage rate
- Leak detection using smoke pencils or infrared imaging
Why Is a Blower Door Test Important?
By providing an objective, quantifiable measurement of a home’s actual air leakage rather than relying on visual inspection or assumption alone, a blower door test gives homeowners and builders genuine data to guide air sealing priorities and verify improvement after work is completed. This measured approach consistently produces better-targeted, more effective air sealing outcomes than unguided efforts.
Many energy codes now require blower door testing as part of new construction compliance verification, reflecting growing recognition that visual inspection alone can’t reliably confirm a home meets air leakage performance targets the way an actual measured test can.
Blower Door Test vs. Energy Audit
A blower door test is one specific diagnostic tool measuring air leakage. An energy audit is the broader, comprehensive assessment process that typically includes blower door testing alongside other evaluation methods like infrared imaging and mechanical system review.