Massachusetts Stretch Energy Code: overview and paths to compliance

2013 Stretch Energy Code  (the 2012 IECC Stretch Code, effective July 2014, will be different)


Adopted in May 2009, the ‘Stretch’ energy code (formerly known as Appendix 115.AA), is an optional energy code for towns and cities in Massachusetts. Every municipality classified as a Green Community is required to adopt the Stretch code. About half of the MA population lives in a Stretch code municipality.

The Stretch code amends the base energy code (currently 2009 IECC) to achieve approximately a 20% improvement in building energy performance. It features a performance code compliance path, as opposed to the more familiar prescriptive path of typical energy codes. The performance path requires a HERS rating to model the energy use of the building. 

Residential Stretch Code Requirements

New residential building -  3-stories or less,  performance requirements:

  • HERS index
    <3,000 ft.sq.: HERS 70 or less  
    >3,000 ft.sq. : HERS 65 or less.
  • Completed Energy Star Homes Thermal Bypass Inspection Checklist
  • Mandatory requirements of the base energy code (2009 IECC)

Existing buildings - performance path requirements:

  • HERS index:
    Renovations  <2,000 ft.sq.  : HERS 85 or less  
    Renovations  >2,000 ft.sq.  : HERS 80 or less

    Additions      <3,000 ft.sq. :  HERS 70 or less  
    Additions      >3,000 ft.sq.  : HERS 65 or less
  • Completed Energy Star Homes Thermal Bypass Inspection Checklist [link]
  • Mandatory requirements of the base energy code (2009 IECC) [link to another page]

Existing buildings - prescriptive path requirements:

  • Any portion of the building modified must be brought up to the base code.
  • New windows, doors, or skylights meet Energy Star 5.0 standards
  • New duct systems outside of thermal boundary must be tested and not exceed 4% leakage to outside.
  • Builders complete relevant portions of the ES Thermal Bypass Inspection Checklist


HERS (Home Energy Rating System) Energy Modeling

The HERS index rates each home on a scale where 0 is a zero-net-energy home , and 100 is a home built to the 2006 base energy code. HERS ratings are performed by HERS raters- independent certified building energy professionals.

The HERS rating involves a detailed energy model of the home, inspections, and diagnostic testing. It is an asset rating, meaning that all fixed elements to the home are factored including thermal boundary details, mechanical systems, ventilation systems, some appliances, renewable energy systems, and lighting fixtures.

For code compliance, the final index (score) is submitted to the local building official during plan review. A good HERS rater will be a resource to the building team through the design and construction processes.

hoose HIS & HERS as your Stretch Code rater

We look forward to being on your team. Included in the rater service is consultation to assist you in cost-effective compliance of the Stretch Code and mandatory requirements of the 2009 IECC.