What is a Blower Door Test? Massachusetts New Construction Guide 2026
A blower door test is a diagnostic tool used to measure the air tightness of new construction buildings in Massachusetts. It is required for all new residential construction in MA Stretch Code municipalities and is a critical component of the HERS Rating process.
How Does a Blower Door Test Work?
A certified technician installs a calibrated fan in an exterior door frame and depressurizes the home to 50 Pascals below outdoor pressure. The amount of airflow required to maintain that pressure is measured in cubic feet per minute (CFM50). This number is then converted to ACH50 (air changes per hour at 50 Pascals) based on the home’s volume.
What is the MA Stretch Code 2021 Blower Door Standard?
New homes in Massachusetts must achieve 3.0 ACH50 or less to comply with the MA Stretch Code 2021. The Specialized Stretch Code requires 2.0 ACH50 or less. Highly efficient homes often achieve 1.0–1.5 ACH50. The old IECC 2018 standard was 3.0 ACH50 — the 2021 code maintained this requirement.
How to Prepare for a Blower Door Test in Massachusetts
For best results: complete all air sealing before the test, seal all penetrations around pipes and wires, install window and door jamb extensions, seal top plates and rim joists, and address any known draft areas. HERS Rating Company provides pre-test consultation to help builders maximize their first-test pass rate.
Blower Door Testing Across Massachusetts
HERS Rating Company performs blower door testing in all 351 Massachusetts cities. Popular locations: Boston, Worcester, Cambridge, Newton, Brookline. Call 617-584-1809 for scheduling.