What Is the Difference Between the MA Stretch Code and the Base Energy Code?
Massachusetts has two residential energy code options: the base energy code (IECC 2021, adopted by the state) and the MA Stretch Code 2021 (an enhanced optional code that over 300 municipalities have adopted). If your city or town has adopted the Stretch Code, it supersedes the base code for new construction.
Key Differences: MA Stretch Code vs Base Code
| Requirement | Base Code (IECC 2021) | MA Stretch Code 2021 |
|---|---|---|
| HERS Rating | Not required | Required (HERS ≤ 55) |
| Blower Door Test | Required (≤ 3.0 ACH50) | Required (≤ 3.0 ACH50) |
| Duct Leakage Test | Required (if ducted) | Required (if ducted) |
| HERS Rater Required | Not required | Required |
| EV Charger Ready | Not required | Required (in some cases) |
| Solar Ready | Not required | Required |
Does the MA Stretch Code Apply in My City?
As of 2026, over 300 Massachusetts cities and towns have adopted the MA Stretch Code. Nearly all cities and towns in Greater Boston, MetroWest, the South Shore, the North Shore, and Western Massachusetts have adopted it. If you are building anywhere near a major population center, there is a very high probability the Stretch Code applies. Check with your local building department to confirm.
Can I Choose the Base Code Instead of the Stretch Code?
No. If your municipality has adopted the MA Stretch Code, it is the applicable building code and you cannot opt out. The Stretch Code replaced the base code for residential new construction in those municipalities. The base code only applies in the handful of communities that have not adopted the Stretch Code.
MA Stretch Code Compliance Services
HERS Rating Company provides full MA Stretch Code compliance services throughout Massachusetts — from plan review and energy modeling to final blower door testing and HERS certification. Learn more about our MA Stretch Code services or contact us for a free quote.
Related Services in Massachusetts
HERS Rating Company is a RESNET-certified, Mass Save-approved HERS Rater serving all 351 Massachusetts cities and towns.
Serving Boston, Worcester, Springfield, Cambridge, Newton, Brookline, and all 351 MA cities. Get a free quote →
MA Stretch Code 2021 vs Base Energy Code: Key Differences
Massachusetts has three energy code tiers: Base Energy Code (IECC 2021), Stretch Code (adopted by 270+ municipalities), and Specialized Stretch Code (most stringent, required in Green Communities). The Stretch Code requires a RESNET HERS Rating, 3.0 ACH50 blower door result, and less than 4% duct leakage. HERS Rating Company provides compliance services for all three code tiers.
How to Know Which Code Applies to Your Project
Check your municipality’s adopted energy code. If they have adopted the Stretch Code (most MA cities have), you need a HERS Rating from a RESNET-certified rater like HERS Rating Company. Call us at 617-584-1809 — we’ll confirm your code requirements for free.