Stretch Energy Code

Stretch Code Overview - (Base code - 2021 IECC with 225 CMR Chapter 22 Mass Amendments)

    The purpose of the stretch energy code is to provide a more energy efficient code alternative for new buildings. It applies to all R-use buildings, of four stories or less above grade, all commercial building over 100,000 square feet, new supermarkets, laboratories and conditioned warehouses over 40,000 square feet.

    The Stretch Energy Code is performance based as opposed to prescriptive, for R-use buildings the new homes/apartments must meet a HERS (Home Energy Rating System) index rating target, based on the total building envelope and mechanical efficiencies. The index rating is calculated by a certified HERS rater using specialized software program who is typically hired by the building contractor. The HERS Rater is certified by the Residential Energy Services Network or RESNET and provides these energy rating and performance testing services.

1. The HERS Rater will produce a Projected Rating document from plans using specialized software which includes the building envelope and mechanicals,  that is submitted with the building permit application. 

  • The maximum HERS index score as of 1/1/2023 is now 52. No fossil fuels in design or a solar array the HERS index is 55, for both the HERS index is 58.
  • Mechanical air - An HRV (heat recovery ventilator) or an ERV (energy recovery ventilator) are now required. HRV's and ERV's are balanced systems with changeable filters which are superior to the old exhaust only option.
  • Future 50amp wiring  for an electric vehicle charging station must be included. One per single family residence and 20% on multi-family residences.

2. The Rater makes a site visit after insulation to inspect what he or she will later have to confirm.

3. Near the projects end the Rater will conduct the required performance testing: a blower door test which measures the buildings leakage; duct testing which measures the duct system leakage and the mechanical air test to help insure good indoor air quality. 

4. With all tests passed and completed the Rater logs the results with the RESNET Registry. The Confirmed Rating document is then submitted to the Building Official.