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Stretch Energy Code Q+A

Q: What is the ‘stretch’ energy code?

A: The ‘stretch code’ is an optional appendix to the Massachusetts building energy code that allows cities and towns to choose a more energy-efficient option. This option increases the efficiency requirements in any municipality that adopts it, for all new residential and many new commercial buildings, as well as for those residential additions & renovations that would normally trigger building code requirements.


Q: How is the stretch code different from the existing ‘base’ energy code?

A: The stretch code appendix offers a streamlined and cost-effective route to achieving approximately 35% better energy efficiency in new residential and commercial buildings than is required by the base energy code. This is largely achieved by moving to a performance-based code, where developers are required to design buildings so as to reduce energy use by a given percentage below base code, rather than being required to install specific efficiency measures.

Developers have flexibility to choose cost effective and appropriately designed solutions. New residential construction must use the performance-based approach and most commercial buildings may instead opt to follow a ‘prescriptive’ route that specifies a set of minimum energy efficiency requirements for different building materials and systems until July 1, 2024.


Q: When do I need a blower door test? Is that just in Stretch Code towns?

A: A blower door, or infiltration test, is required by code for any dwelling unit in buildings 5 stories or less. 6 story or more buildings also require infiltration testing, but at a different threshold. HVAC or duct testing is also required, along with ventilation.


Q: How is the stretch code implemented and enforced?

A: Implementation and enforcement of the code is similar to existing code, where the developer is responsible for submitting documentation of compliance to the building inspector for review, and the building inspector conducts a plan and site review. The actual testing is performed by a certified or approved third party (Home Energy Raters).


Q: What is the role of a building code official and a HERS Rater for residential projects?

A: Residential buildings meeting the stretch code through a HERS rating and EPA thermal bypass or thermal enclosure checklist require independent certification by a HERS Rater (Home Energy Raters). The rater will produce a report detailing the energy systems in the building and will provide a HERS index score, together with proof of whether the home qualifies for any federal tax credits. Submission of the HERS report, together with a completed Energy Star Thermal checklist, are the steps required to demonstrate compliance with the energy portions of the code, and must be submitted to the local building inspector prior to receiving a certificate of occupancy. In this way the local inspector retains their oversight role but the additional energy requirements do not place a significant additional burden on their time.


Q: How do I meet the residential stretch code for new homes?

A: The Stretch Energy Code (2021 IECC w/ MA Amendments) has changed as of January 1, 2023, for residential buildings 3 stories or less. 4+ story residential buildings will remain on the current code until the 2023 Multifamily & Commercial Code goes into effect on July 1, 2023It is important to note that there is no grace period with the new code changes.

This new Energy Code brings some substantial updates/changes which may affect how you build. There is an overall push to remove fossil fuels from new buildings and higher HERS Ratings will be allowed for all-electric buildings.

HIGHLIGHTS OF CHANGES (applies to both new construction AND renovation/addition projects):

– HERS 52 required if any propane or natural gas is used in the building
– HERS 55 allowed if the home is all-electric
– HERS 55 (Fuel + Solar) or HERS 58 (Electric + Solar) also allowed
– 1 EV-Ready space and wiring per house required (EV-Ready also required for multi-family projects but requirements vary)
– ERV or HRV will now be required. Bath fans no longer meet the requirement for whole- house mechanical ventilation. There are some models we recommend using (with lower wattage) that help the HERS Rating, but you can use any brand you would like. You will still need to meet the required CFM of ventilation.
– HVAC duct leakage testing is now required for all systems, even if all ducts are within the conditioned envelope
– HERS Ratings will be required for additions over 1,000 sq ft and/or over 50% of the original structure (Level 3 Alteration per IEBC)
– Starting July 1, 2023, municipalities can vote to approve the “Specialized Stretch Code” which will require Net Zero/Zero Energy, solar, and lower HERS Ratings. Municipalities that opt-in to this are likely to provide a 6-9 month grace period. We will make sure to let you know when we hear of municipalities approving this provision.


– On July 1, 2024, HERS requirements drop to HERS 42 for buildings with any gas/fuel or HERS 45 for all electric homes/buildings


Q: Does the stretch code apply to minor additions to existing buildings?

A: HERS Ratings will be required for additions over 1,000 sq ft and/or over 50% of the original structure (Level 3 Alteration per IEBC). Additions to existing buildings that are large enough to require code compliance are treated in the same way as new construction for commercial buildings, and in the same way as renovations in residential buildings.


Q: What categories do multi-family residential buildings fall into?

A: Residential multi-family buildings that are above 100,000 square feet and at least four stories tall have to follow the same performance path (20% better than the ASHRAE standard 90.1-2007) as other commercial buildings larger than 100,000 square feet. Residential buildings below 100,000 square feet and at least four stories tall are classified with commercial buildings between 5,000 and 100,000 square feet. Multi-family homes with one to three stories of any size fall under the residential stretch code standards. In the rare case of a multi-family building of three stories or less that is larger than 100,000 square feet, the developer may elect to be treated either.