A blower door test is one of the most important diagnostics performed during a HERS rating. It measures how much air leaks out of a home, which directly affects comfort, energy bills, and code compliance.
How the Test Works
A powerful calibrated fan is mounted in an exterior doorway and depressurizes the house. As air is pulled out, outside air rushes in through every crack and gap. By measuring the airflow needed to hold a set pressure, the rater calculates the leakage rate, usually expressed in air changes per hour at 50 pascals, or ACH50.
What the Numbers Mean
A lower ACH50 means a tighter, more efficient home. Massachusetts energy code sets maximum leakage thresholds that new construction must meet. A leaky house wastes conditioned air, invites drafts and moisture problems, and is far more expensive to heat through a New England winter.
Finding and Fixing Leaks
During the test, a rater can use the depressurized condition to locate specific leaks around rim joists, top plates, recessed lights, plumbing penetrations, and window frames. Sealing these areas before the final test is the most cost effective way to improve performance.
Scheduling Your Test
Timing matters. We recommend a preliminary test once the air barrier is complete but before drywall, so any problems can be corrected easily. Contact us to coordinate testing around your build schedule.