Massachusetts Energy Code Stretch Code Specialized Opt-In Code HERS / ERI

Massachusetts Stretch Energy Code: What It Is & How We Help You Pass

A practical, builder-friendly guide to the MA Stretch Energy Code and the Municipal Opt-In Specialized Energy Code — plus exactly how HERS Rating Company supports plan review, energy modeling, HERS/ERI ratings, testing, and documentation from permit to final inspection.

Fewer change orders by locking specs early

Pass inspections with the right compliance pathway

Score guidance to hit ERI/HERS targets cost-effectively

Testing + paperwork handled start-to-finish

On this page: What is the Massachusetts Stretch Energy Code?

Massachusetts has a statewide “Base” energy code, and municipalities can choose to adopt a higher-performance option called the Stretch Energy Code. In addition, some municipalities have adopted an even more demanding option called the Municipal Opt-In Specialized Energy Code (often shortened to “Specialized Opt-In”).

Important: The code you must follow is based on where the project is permitted. Two towns next to each other can have different adoption status and different compliance expectations.

Base vs Stretch vs Specialized Opt-In: what’s the difference?

Base Energy Code (Statewide default)

This is the minimum energy-efficiency standard used statewide unless a municipality has adopted Stretch or Specialized requirements. Massachusetts aligns its code to the IECC (with MA amendments).

Stretch Energy Code (Municipal adoption)

An enhanced performance-focused option that typically requires better envelope performance, tighter air-sealing, and more attention to whole-building outcomes (not just prescriptive checklists).

Specialized Opt-In Code (Municipal adoption)

Built to move new buildings toward long-term emissions goals. In many cases, it increases expectations for building performance and often pushes electrification strategies (with added requirements if fossil fuel equipment is used).

On low-rise residential projects, Massachusetts commonly allows (and in many Stretch/Specialized communities effectively expects) performance compliance using an ERI / HERS pathway.

Why HERS / ERI matters (and when you need it)

A HERS rating (Home Energy Rating System) is a standardized scoring method used to quantify a home’s energy performance. In code terms, it’s often tied to the Energy Rating Index (ERI) compliance option.

When HERS/ERI is commonly required

• • New construction low-rise residential in Stretch/Specialized municipalities

• • Many major renovations, additions, and “gut rehab” scopes when the Stretch/Specialized trigger applies

• • Projects using performance compliance rather than purely prescriptive checklists

What inspectors typically want to see

• • Preliminary compliance documentation / modeling assumptions

• • Midpoint verification (insulation + air sealing quality)

• • Final test results (blower door, and duct leakage when applicable)

• • Final HERS/ERI documentation and supporting equipment details as required

The fastest way to lose time and money is to treat HERS as “paperwork at the end.” The best results happen when the HERS/ERI strategy is built into the project from plans through finish.

How HERS Rating Company helps you pass the Stretch Code

1) Plan review + compliance roadmap (before ordering anything)

We review plans and specs that drive compliance and score risk, including:

• • Envelope & insulation strategy (walls/roof/foundation, key transitions)

• • Air-sealing details and realistic ACH50 targets

• • Window specs (U-factor / SHGC) aligned to your pathway and model

• • HVAC approach, ventilation strategy (ERV/HRV), and equipment selections

• • Domestic hot water strategy (heat pump water heater, tankless where applicable to the pathway)

• • Controls, appliances, and other items that impact modeled outcomes or program requirements

Deliverable: a builder-friendly checklist you can build to without surprises.

2) Energy modeling + HERS/ERI target coaching

We run energy modeling and provide cost-effective recommendations to hit targets with fewer expensive last-minute changes.

• • “Best bang-for-buck” upgrades that move the score

• • Value engineering that protects compliance

• • Coordinate substitutions (windows, HVAC, ERV/HRV) without breaking your model

3) Midpoint verification (the make-or-break stage)

We verify key details before drywall so you don’t fail at the finish line.

• • Insulation inspection & installation quality checks

• • Air sealing review at penetrations, rim joists, attic transitions, chases

• • Ventilation layout review and “commissioning-ready” guidance

4) Final testing + documentation package

• • Final blower door testing

• • Duct leakage testing (when required/applicable)

• • Equipment verification support (model/serial capture where needed)

• • Final HERS/ERI documentation aligned to the adopted code pathway

5) Consulting for tough projects

If your project is complex (multi-phase renovation, mixed systems, challenging envelope, tight schedules), we help with:

• • Scope planning to avoid triggering unexpected requirements

• • Field troubleshooting and re-test strategy

• • Coordination with designers, HVAC contractors, and inspectors

Want a fast answer on your project?

Tell us your city/town, project type (new build / addition / gut reno / ADU), and system plan (all-electric vs mixed-fuel). We’ll map the likely code pathway and the smartest compliance plan.
Contact HERS Rating Company

Common Stretch/Specialized failure points (and how we prevent them)

Late equipment swaps

Swapping HVAC/ERV/HRV/DHW models after the model is built can break compliance. We help you review substitutions before purchase.

Wrong windows ordered

Window U-factor/SHGC mismatches are one of the most expensive “oops” mistakes. We lock window targets early and confirm submittals.

Air sealing ignored until the end

Air sealing must be designed, scheduled, and verified at midpoint—especially at transitions and penetrations—so the final blower door passes.

Ventilation installed but not “right”

ERVs/HRVs need correct ducting, controls, and commissioning. We guide layouts at midpoint so the final verification is clean.

Which Massachusetts municipalities use Stretch or Specialized?

Massachusetts publishes an official energy code adoption by municipality document showing which communities are Base, Stretch, and which have adopted the Specialized Opt-In code. This is the most reliable way to confirm your project’s rules before you build.

How to confirm your town’s adoption status

1. 1. Find your municipality on the state’s adoption list

1. 1. Confirm whether it’s Base, Stretch, or Specialized Opt-In

1. 1. Align your compliance pathway (often ERI/HERS for low-rise residential)

All Massachusetts cities & towns (official directory)

Massachusetts has 351 cities and towns. If you’re unsure of the official municipal name (or want the town website), use the state directory and then cross-check adoption status.

We serve all of Massachusetts: Greater Boston, MetroWest, North Shore, South Shore, Central MA, Western MA, Cape & Islands — including projects in Base, Stretch, and Specialized Opt-In municipalities.

FAQ: Massachusetts Stretch Energy Code & HERS ratings

Is the Stretch Code required everywhere in Massachusetts?

No. The Base Energy Code applies statewide, but Stretch and Specialized Opt-In rules apply only in municipalities that have adopted them. Always confirm your town’s adoption status before setting specs.

Do I need a HERS rater for my project?

Many low-rise residential projects in Stretch/Specialized communities use an ERI/HERS compliance pathway that requires third-party testing and documentation. If your project needs HERS/ERI, you’ll typically have midpoint verification and final testing requirements.

What’s the #1 thing I should do first?

Confirm the municipality’s adoption status (Base vs Stretch vs Specialized), then do a plan review and lock windows/HVAC/ventilation/DHW decisions early so you don’t pay for rework later.

Where do I find the “official” code language?

Massachusetts publishes 225 CMR regulations for residential and commercial energy codes, plus supporting code language documents and guidance. We use those sources to align your compliance plan to what inspectors expect.

Contact HERS Rating Company

HERS Rating Company — HERS/ERI Ratings • Energy Modeling • Stretch/Specialized Consulting • Blower Door • Duct Testing

• • Phone: 617-584-1809

• • Email: Hersratingcompany@gmail.com

• • Service area: All Massachusetts municipalities,

• • A: Abington, Acton, Acushnet, Adams, Agawam, Alford, Amesbury, Amherst, Andover, Aquinnah, Arlington, Ashburnham, Ashby, Ashfield, Ashland, Athol, Attleboro, Auburn, Avon, Ayer
    B: Barnstable, Barre, Becket, Bedford, Belchertown, Bellingham, Belmont, Berkley, Berlin, Bernardston, Beverly, Billerica, Blackstone, Blandford, Bolton, Boston, Bourne, Boxborough, Boxford, Boylston, Braintree, Brewster, Bridgewater, Brimfield, Brockton, Brookfield, Brookline, Buckland, Burlington
    C: Cambridge, Canton, Carlisle, Carver, Charlemont, Charlton, Chatham, Chelmsford, Chelsea, Cheshire, Chester, Chesterfield, Chicopee, Chilmark, Clarksburg, Clinton, Cohasset, Colrain, Concord, Conway, Cummington
    D: Dalton, Danvers, Dartmouth, Dedham, Deerfield, Dennis, Dighton, Douglas, Dover, Dracut, Dudley, Dunstable, Durham
    E: East Bridgewater, East Brookfield, East Longmeadow, Eastham, Easthampton, Easton, Edgartown, Egremont, Erving, Essex, Everett
    F: Fairhaven, Fall River, Falmouth, Fitchburg, Florida, Foxborough, Framingham, Franklin, Freetown
    G: Gardner, Georgetown, Gill, Gloucester, Goshen, Gosnold, Grafton, Granby, Granville, Great Barrington, Greenfield, Groton, Groveland,
    H: Hadley, Halifax, Hamilton, Hampden, Hancock, Hanover, Hanson, Hardwick, Harvard, Harwich, Hatfield, Haverhill, Hawley, Heath, Hingham, Hinsdale, Holbrook, Holden, Holland, Holliston, Holyoke, Hopedale, Hopkinton, Hubbardston, Hudson, Hull, Huntington
    I: Ipswich
    J: Jamaica Plain 
    K: Kingston
    L: Lakeville, Lancaster, Lanesborough, Lawrence, Lee, Leicester, Lenox, Leominster, Leverett, Lexington, Leyden, Lincoln, Littleton, Longmeadow, Lowell, Ludlow, Lunenburg, Lynn, Lynnfield
    M: Malden, Manchester-by-the-Sea, Mansfield, Marblehead, Marion, Marlborough, Marshfield, Mashpee, Mattapoisett, Maynard, Medfield, Medford, Medway, Melrose, Mendon, Merrimac, Methuen, Middleborough, Middlefield, Middleton, Milford, Millbury, Millis, Millville, Milton, Monson, Montague, Monterey, Montgomery, Mount Washington
    N: Nahant, Nantucket, Natick, Needham, New Ashford, New Bedford, New Braintree, New Marlborough, New Salem, Newbury, Newburyport, Newton, Norfolk, North Adams, North Andover, North Attleborough, North Brookfield, North Reading, Northampton, Northborough, Northbridge, Northfield, Norton, Norwell, Norwood
    O: Oak Bluffs, Oakham, Orange, Orleans, Otis, Oxford
    P: Palmer, Paxton, Peabody, Pelham, Pembroke, Pepperell, Peru, Petersham, Phillipston, Pittsfield, Plainfield, Plainville, Plymouth, Plympton, Princeton, Provincetown
    Q: Quincy
    R: Randolph, Raynham, Reading, Rehoboth, Revere, Richmond, Rochester, Rockland, Rockport, Rowe, Rowley, Royalston, Russell, Rutland
    S: Salem, Salisbury, Sandisfield, Sandwich, Saugus, Savoy, Scituate, Seekonk, Sharon, Sheffield, Shelburne, Sherborn, Shirley, Shrewsbury, Shutesbury, Somerset, Somerville, South Hadley, Southborough, Southbridge, Southwick, Spencer, Springfield, Sterling, Stockbridge, Stoneham, Stoughton, Stow, Sturbridge, Sudbury, Sunderland, Sutton, Swampscott, Swansea
    T: Taunton, Templeton, Tewksbury, Tisbury, Topsfield, Townsend, Truro, Tyngsborough, Tyringham
    U: Upton, Uxbridge
    V: Wakefield, Wales, Walpole, Waltham, Ware, Wareham, Warren, Warwick, Washington, Watertown, Wayland, Webster, Wellesley, Wellfleet, Wendell, Wenham, West Boylston, West Bridgewater, West Brookfield, West Newbury, West Springfield, West Stockbridge, West Tisbury, Westborough, Westfield, Westford, Westhampton, Westminster, Weston, Westport, Westwood, Weymouth, Whately, Whitman, Wilbraham, Williamsburg, Williamstown, Wilmington, Winchendon, Winchester, Windsor, Winthrop, Woburn, Worcester, Worthington, Wrentham
    Y/Z: Yarmouth

The Massachusetts Stretch Energy Code is an optional, higher-performance energy code that municipalities can adopt in place of the statewide Base Energy Code. It is codified under 225 CMR 22.00 (Residential) and 225 CMR 23.00 (Commercial) and is based on the 2021 International Energy Conservation Code (IECC) with Massachusetts-specific amendments. The Stretch Code was developed to improve building energy efficiency beyond minimum statewide standards and to help the Commonwealth meet its greenhouse gas reduction requirements under the Global Warming Solutions Act. Today, the majority of Massachusetts municipalities — more than 300 of the state’s 351 cities and towns — have adopted the Stretch Energy Code, making it the standard compliance pathway for most new residential construction across the state.

For low-rise residential buildings, the Stretch Code commonly relies on a performance-based compliance pathway using the Energy Rating Index (ERI), verified through a certified HERS (Home Energy Rating System) rating. This approach requires energy modeling during the design phase and third-party field verification during construction. Projects must typically include blower door testing to measure air leakage, confirmation of insulation installation, and verification that HVAC, ventilation, and water heating systems match the approved specifications. Compared to the Base Energy Code, the Stretch Code generally requires tighter building envelopes, improved insulation strategies, higher efficiency mechanical systems, and documented performance testing before a final certificate of occupancy is issued.

HERS Rating Company plays a critical role in helping builders, architects, and homeowners comply with the Massachusetts Stretch Energy Code. We begin with a detailed plan review to determine the correct compliance pathway and identify the most cost-effective strategy to achieve the required ERI/HERS target. Our team performs energy modeling to guide decisions on insulation levels, window specifications, HVAC efficiency, ventilation systems, and water heating equipment before materials are ordered. During construction, we provide midpoint inspections to verify insulation quality and air sealing practices, helping prevent costly failures at final testing. At project completion, we conduct blower door and duct leakage testing (when required) and provide the official HERS/ERI documentation needed for code compliance and final inspection approval. By integrating compliance strategy from the design phase through final verification, HERS Rating Company ensures projects meet Stretch Code requirements efficiently, predictably, and without last-minute surprises.