Blower Door Testing in Granville, MA — ACH50 Requirements & What to Expect (2026)
The Granville air-leakage limit, how the blower door test works, what happens if you don’t pass, and how to book a certified test that satisfies your building department.
Blower Door Quick Facts — Granville
- Granville new homes must test at 3.0 ACH50 or lower (air changes per hour at 50 pascals).
- The blower door test is required to demonstrate energy-code compliance and to complete a HERS rating.
- It must be performed and documented by a certified rater using calibrated equipment.
- A failing result can be re-sealed and re-tested — we help pinpoint the leaks.
What the Granville Blower Door Test Measures
A blower door is a calibrated fan mounted in an exterior doorway that depressurizes the home to 50 pascals. The equipment measures how much air leaks through the building envelope, expressed as ACH50 — air changes per hour at 50 Pa. Tighter homes lose less conditioned air, cost less to heat and cool, and are more comfortable. In Granville, the Stretch Code caps new residential construction at 3.0 ACH50.
Granville Air-Leakage Requirement
| Building type | Maximum air leakage | Verification |
|---|---|---|
| New single-family home | ≤ 3.0 ACH50 | Blower door test at completion |
| Townhouse / attached dwelling | ≤ 3.0 ACH50 | Per-unit test |
| Addition (treated as dwelling) | ≤ 3.0 ACH50 | When conditioned space is added |
This limit is part of the Stretch Code that Granville enforces and is checked before your certificate of occupancy.
How the Test Works
1. Set Up
- Seal intentional openings
- Mount calibrated fan
- Close windows & doors
2. Depressurize
- Fan pulls to 50 Pa
- Measure airflow (CFM50)
- Convert to ACH50
3. Report
- Pass/fail vs 3.0
- Locate leaks if high
- Documented result
If Your Granville Home Doesn’t Pass
A high reading isn’t the end — it’s a punch list. Common leak points are rim joists, top plates, recessed lights, and penetrations. We identify the sources, you seal them, and we re-test. Getting the blower door done before insulation is covered makes fixes far cheaper.
Book Testing in Granville
We provide certified blower door testing across Granville and pair it with your HERS rating and duct leakage testing. For the full code picture, see Granville energy code help.
Quick Answers — Granville Blower Door Testing
Book a blower door test in Granville.
Talk to a certified Massachusetts HERS rater and get a free, no-obligation quote.
Call (617) 571-4368 Get a Free Quote