Barnstable, MA Energy Code Compliance — Base Energy Code & HERS Requirements (2026)
Everything a builder, architect, or homeowner in Barnstable needs to pass the current Massachusetts energy code — explained in plain English by a certified HERS rater.
Quick Facts for Barnstable
- Barnstable is on the Base Energy Code (225 CMR 22.00 / 51.00 (base code)).
- New homes must be third-party HERS-rated and hit the index targets below.
- A blower door test (≤3.0 ACH50) and duct leakage test are required to demonstrate compliance.
- Both all-electric and mixed-fuel paths are available.
What Energy Code Is Barnstable On?
Barnstable enforces the Base Energy Code of the Massachusetts energy code (225 CMR 22.00 / 51.00 (base code)). The base energy code applies here; new homes still require HERS verification but without the added Stretch/Specialized performance targets.
Compliance is demonstrated through the HERS (Home Energy Rating System) performance pathway — the code option nearly all Barnstable builders use — which requires a certified rater to model the design, inspect during construction, and verify final performance with diagnostic testing.
HERS Index Targets in Barnstable
The lower the HERS Index, the more efficient the home (a HERS 0 is net-zero). Your maximum allowable score depends on the project type and whether it is all-electric or mixed-fuel:
| Project type | Mixed-fuel HERS max | All-electric HERS max |
|---|---|---|
| New single-family home | 42 | 45 |
| New home w/ solar + pre-wiring pathway | 45 | 48 |
| Addition (>1,000 sq ft) | 65 | 70 |
| Accessory Dwelling Unit (ADU) | 52 | 55–58 |
Required Diagnostic Testing
Two on-site tests verify the modeled performance is real. Both must be performed and documented by a certified rater before your Barnstable building department will sign off:
| Test | Requirement | Why it matters |
|---|---|---|
| Blower door (air leakage) | ≤ 3.0 ACH50 | Verifies the building envelope is sealed tight |
| Duct leakage (CFM25) | ≤ 4 CFM25 per 100 sq ft | Confirms conditioned air isn’t lost to unconditioned space |
The Barnstable Compliance Path, Step by Step
How We Help Barnstable Builders & Homeowners
We are a certified Massachusetts HERS rating company serving Barnstable and the surrounding area. We handle the full energy-code compliance process: HERS rating & energy modeling, blower door testing, and duct leakage testing — all documented for your building department.
Quick Answers — Barnstable Energy Code
Building in Barnstable? Get your energy-code plan today.
Talk to a certified HERS rater about your project — no obligation.
Call (617) 571-4368