2015 IECC and the updated Massachusetts Stretch Code

2015 IECC energy code expected mid 2016 

note: These thoughts are based on the recently released draft MA Residential Code 9th edition Amendments to the IRC 2015.  Download here.

Very similar to the 2012 IECC code. ERI performance path added to base code, renewable energy tradeoffs.

Aside from the addition of the 'ERI' (HERS Rating or PHIUS) path option, the differences are minor. In fact so minor that I'll direct you to this summary from the Online Code & Advocacy Network. Most of the re-writes were intended to clarify existing language and simplify compliance. Yay.

In Massachusetts we have already adjusted to the performance path, since the 2012 IECC MA Amendments and Stretch Code already incorporated a HERS rating option (2012 IECC) and a requirement (Stretch Code). The ERI addition shouldn't ruffle any feathers. Stretch Code projects have to follow the ERI path, and base code projects have the option to.

The ERI path is an alternative to the 'prescriptive' aspects of the code (see 402.1 table below) . This provides more flexibility for meeting code, not to mention Mass Save New Construction rebate opportunities (IMO, a no brainer for every new residential build). 

Here are the prescriptive 2015 IECC R-values. With the ERI path, these do not need to be followed.

(The MA amendments drop the U-factor for CZ 5 to < U-0.30 )

(The MA amendments drop the U-factor for CZ 5 to < U-0.30 )

Here are the updated HERS index limits, including renewable energy tradeoffs.

The 9th edition draft HERS index limits. 

The 9th edition draft HERS index limits. 

The maximum HERS index is 55 . This is a big drop from 70, in the current 2009 IECC Stretch Code. This HERS index threshold is the same for base code and Stretch Code communities. So effectively there is no 'stretch' to the Stretch Code. At HIS & HERS Energy Efficiency we are okay with that. HERS 55 is a fair target. 

Consistency between the Stretch Code and the base code.... at last!

The biggest impact in Massachusetts is that as soon as the 2015 IECC is adopted, the Stretch Code will be updated. No longer will the Stretch Code point to the 2009 IECC (approximately 15% less efficient than the 2015). This should relieve a lot of confusion as mandatory code requirements- especially whole house airtightness and duct leakage limits- will be consistent. Builders will no longer [have reason to] complain that their friend's house in the next town could be twice as leaky. In my book code consistency and consistency of enforcement is more important than increased stringency, so this is very refreshing. 

Both the base code and the Stretch Code will require <3 ACH50 whole house leakage and <4% total leakage duct tightness limits (w/ handler) .

This is consistent with the current 2012 IECC base code, but is a big improvement over the 2009 IECC that some CT builders are fussing about and that most of the nation is working under (<7 ACH50 and <12% total leakage) 

Stretch Code gets shortened from 12 pages to 1page.

If the residential project is in a Stretch Code town, then the ERI performance path of the base energy code with MA Amendments must be followed. Per the chart above, HERS 55 is the threshold, with no adjustment for home size. There is also no longer any reference to the Energy Star Thermal Bypass Inspection Checklist, the previously required air barrier checklist. 

Download the Stretch Code excerpt (N1106.1) from the Mass 9th Residential Draft 2015-06-23 version here. 

Simpler is better, even though there is less 'stretch'. 

I am hopeful that the updated Stretch Code that points to the current base code, will make life easier for all involved. There will be much less variation of what is acceptable building practices. Since MA has been working to the 2012 IECC already, this code shift is much easier than other states i

As a HERS rater who works mostly in Western MA, both Stretch Code and base code towns, I find the changes to be fair and practical. HERS 55 is a good jump from HERS 70, yet is not necessarily difficult or expensive to achieve. To meet <55, there is no need for european high performance building materials. Most mechanical equipment off the shelf is high efficiency. Energy Star rated appliances are cost effective, LEDs are cheap (or free from utilities). There are many ways to design and build a home to meet this. Good design is important - be careful purchasing house plans that are not designed for this code region - crazy roof lines, whacky knee-walls, and small framing dimensions will require more specific thermal enclosure approaches to meeting code. 

To meet the <3 ACH50 whole building airtightness requirement, simple awareness of air-barrier design and integrity is needed. It is difficult to meet this by mistake using inexpensive materials (fiberglass, 2x6 framing), but add a little bit of thinking and it's darn easy. 

Achieving <4% total leakage for duct systems is difficult. I always recommend including all ducts in the thermal enclosure so they don't need to be tested. Or make sure the installer is aware of how to meet the tightness threshold (hint: mastic & tape!) and will guarantee it passes.

Contact us for any of your code questions. We provide Certified HERS ratings and technical support for builders, designers, and property owners to help pass energy code and to leverage available rebates.