Massachusetts 2015 IECC & Stretch Energy Code

The 9th Edition of the MA State Building Code came into full effect as of January 1, 2018.

What does this mean?

All New Residential and Full gut-renovations are now subject to Massachusetts amended version of the 2015 IECC (International Energy Conservation Code) Base or Stretch Energy Code. This is an update from the previous 2012 IECC.

What you need know about Massachusetts 2015 IECC.

Stretch Code:

To date approx. 80% of towns & cities throughout Massachusetts have adopted the Stretch Energy Code (click here to view map). The stretch code now directly mirrors the performance path of the 2015 IECC making energy upgrades more cost effective than the previous 2009 IECC.

Key changes:

A drop in the maximum HERS index target! You are now required to achieve no more than a HERS 55. This is a 15 point drop from the previous HERS Index target of 70 making homes and buildings roughly 15% more efficient than the previous 2009 IECC requirements.

The Stretch Energy Code is now fully aligned with the 2015 IECC ("ERI") path as explained in the "MA 2015 IECC base code" section below. Builders/homeowners now have the opportunity to choose from one of the following compliance methods:

  1. RESNET Certified HERS Rating: This is the most common path with minimal costs to achieve (click here for a description of a HERS Rating). *Tip: Make sure to involve a HERS rater early on in the design process. With a lower (more efficient) HERS Rating of 55 to reach, this will help prevent code failures and costly mid-construction repairs and retesting fees.

  2. Energy Star v.3.1 certification: With the help of a HERS Rater, builders are able to apply beyond code applications to their home to meet a higher level of energy efficiency.

  3. Passive House Institute US ("PHIUS")+2015: North Americas Passive Building standard software, where specific space heat demand is less than or equal to 10 kBTU/ft2/year.

Massachusetts base and stretch energy code now allows for a combination of renewable energy trade offs which will increase the maximum HERS Index Target of 55. The table below describes these trade offs.

Massachusetts 2015 IECC Base Code.

Whether you are building a new home, full gut-remodel, or adding an addition, parts of the Massachusetts 2015 IECC base code now applies.

Key Changes:

All projects must now comply with one of the following to meet code requirements:

  • 2015 IECC Prescriptive path: New residential construction outside of a stretch code territory or existing renovations and additions, have the ability to follow a prescriptive table and does not require a full HERS Rating. This is a cut and dry pathway towards compliance and involves following parts of the (R402.1.2 table) as well as all mandatory and prescriptive requirements of the 2015 IECC. Some of those requirements include: blower door testing result of 3 ACH50, 4% total duct leakage (w/air handler), and following the Energy Star's "Thermal Bypass Inspection checklist prior to dry-wall". Refer to chapter 11 of the MA building code to see all requirements.

2015 IECC Prescriptive minimum R-value chart.
MA 2015 IECC Prescriptive Path table. MA is climate zone 5. MA addendum: Windows U-factor: 0.30.
  • Energy Rating Index compliance (performance path alternative): The ("ERI") path is referring to the RESNET HERS Rating or ("PHIUS") Passive House standard. This is the compliance path Stretch Code communities follow. As explained in the stretch code section the maximum HERS Rating Index to comply is 55 or less.

A Key Feature in following the ("ERI") or HERS Rating path for compliance is that a builder/homeowner has the ability to choose specific energy efficiency measures to install. Unlike the "Prescriptive Path", where you have to follow mandatory insulation and fenestration requirements. The "ERI" Path requires a home to meet a HERS Rating Target, giving the flexibility to design a residential building's energy measures i.e. windows, insulation levels throughout the building, heating & cooling equipment, etc.

In summary.

We hope this small break down of the Massachusetts Base and Stretch Energy Code was helpful. Here at Delta Enclosures we are dedicated to finding the right energy solution for every project, New or Existing. Give us a call today (508) 397-3730 or click Get Started on our home page "From Concept to Completion, we are your Energy Code partner"


Brandon Velasquez | Principal / HERS Rater

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