Glossary · Testing & air leaks
Blower door test
Also called: blower door · air leakage test · airtightness test · depressurization test · fan door test
A test that uses a powerful, calibrated fan in an outside doorway to pull air out of the house and measure how leaky it is.
What it means
The auditor seals the fan into an exterior door frame and lowers the indoor air pressure, so outside air rushes in through every crack and gap. The fan's airflow at a standard pressure of 50 pascals (see 50 Pa) gives the home's leakage as CFM50 or ACH50. While the fan runs, the auditor can find leaks with a smoke pencil or infrared (thermal) imaging, and a repeat test after air sealing shows how much was fixed.
Why it matters in an audit
It turns 'my house feels drafty' into a number you can compare and set targets for, and it helps size heating and cooling equipment and decide whether the home needs mechanical ventilation.
Typical numbers
Reference values with their sources. Your auditor’s report gives the figure for your own house.
| What | Value | Source |
|---|---|---|
| Standard test pressure | 50 Pa (about 0.2 inch of water column) | energycodes.gov ↗ |
In the United States
Where a state has adopted the 2012 or newer IECC, new homes must pass a blower door test. Raters use procedures such as ANSI/RESNET/ICC 380.