Blower Door Testing in Waltham, MA — ACH50 Requirements & What to Expect (2026)
The Waltham 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 — Waltham
- Waltham 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 Waltham 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 Waltham, the Stretch Code caps new residential construction at 3.0 ACH50.
Waltham 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 Waltham 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 Waltham 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 Waltham
We provide certified blower door testing across Waltham and pair it with your HERS rating and duct leakage testing. For the full code picture, see Waltham energy code help.
Quick Answers — Waltham Blower Door Testing
Book a blower door test in Waltham.
Talk to a certified Massachusetts HERS rater and get a free, no-obligation quote.
Call (617) 571-4368 Get a Free Quote