RESNET HERS changes - Standard 380

HERS ratings technical standards just changed.  What does it mean for you? Costs may go up, duct testing gets more complex, passing airtightness requirements gets harder...oh my.  For builders, code officials, and property owners, this is a high level summary of a few of the changes. These changes are effective for ALL Certified HERS ratings completed on homes permitted [edited to reference permit date]  after July 1, 2018

As part of an effort to increase consistency with HERS ratings, RESNET updates it’s standards to include:  ANSI/RESNET/ICC 380-2016 Standard for Testing Airtightness of Building Enclosures, Airtightness of Heating and Cooling Air Distribution Systems, and Airflow of Mechanical Ventilation Systems. Yeah, and you think you have a branding problem.  There is a lot here that will impact how HERS ratings are completed for homes permited after July 1, 2018.  

A slide deck with larger font and a complete summary of changes can be found here from the Deptmnt of Energy


I don’t feel great about these changes. By adding more terminology and more detailed testing procedures, I expect that ratings will become less consistent not more consistent.  IMO, a better solution would be to require raters to explain their rationale for determinations around testing volumes and inside/outside components, such as infiltration volume/ conditioned floor area. Or even better, like PHIUS, standardize the use of Sketchup for more streamlined oversight and communication.  Standard 380 replaces Chapter 8 and it is here- there is no use grumbling about it. 


For code compliance single-point blower door tests, results must be multiplied by 110% before calculating ACH50 result (whole house air change per hour). For multi-point blower door testing (software assisted blower door testing at pressure reading between 10 and 60 pascals) this 10% ‘adder’ is not required. Single point blower door testing procedures are slightly simplified. 

SO WHAT? -  For most builders in 2012-2018 IECC jurisdictions, 3 ACH50 is not difficult anymore. If you consistently build around 2.5 ACH50 or lower, I would not be concerned. For homes that are very close to the 3 ACH50 code required tightness level, paying for the more complex ‘multi-point’ blower door test procedure may be worth it. Or, consult with your rater where additional airsealing opportunities can be had. A whole house air leakage result of 2.7 or 3 ACH50 is not hard. It doesn’t require spray foam or European tapes with funky names. Just have a plan and make sure Jo Sub is on board. 


First a review of 2012/2015/2018 IECC code requirements for context: If the home has any portion of the forced air heating/cooling duct system outside of insulated space, the entire duct system(s) needs to be tested to a level of <4 CFM 25 per 100 sq. ft of conditioned floor area. This is no joke. The result of this strict target is that ducts are tighter and more commonly located ‘inside’ of the insulated volume of the home. This is a good thing. The Standard 380 changes how we perform duct leakage testing, and is now slightly more complicated and time consuming.

Duct tightness testing MUST be completed at the air handler, not a central return register. Exception: 3 or less returns in entire house AND <50 CFM of total system leakage (very tight ducts) OR if there are access/safety issues that compromise the rater’s ability to test at the cabinet.

Also, the ENTIRE SYSTEM must be installed for the test. No longer is a mid-point, duct only/no handler test allowed to demonstrate code compliance. Of course testing at this phase in construction is good idea to verify tightness, while ducts are still accessible.
Some practical changes have been made concerning where to tape off duct registers. It is now okay to tape inside boot if floors have carpets or grills are not installed.

SO WHAT? - Requiring testing at the cabinets will likely add cost to duct testing. Hopefully the benefits and gains in consistency, outweigh this.  It is unclear to me how ducted heat pumps will be tested as a central return is often the only access point to the heat pump cassette.  This is another reason to avoid duct testing by moving all ducts inside of insulated space or going ductless. 


  • Conditioned Space Volume
  • Unconditioned Space Volume
  • Infiltration Volume
  • Conditioned Floor Area

Conditioned floor area and home volumes have a large impact on HERS rating and airtightness testing results. Without getting too deep, for insulated spaces to be considered part of the ‘conditioned space volume’, the heating/cooling equipment needs to be sized so temperature set points (68 heating, 78 cooling) can be met, verified by a Manual J sizing report.

This shouldn’t be a problem as long as there are access doors/hatches to insulated attics and insulated semi-finished basement with supply registers. Modern heating/cooling equipment can modulate effectively, rarely are they undersized for this to be a problem. Simple volumes and thermal boundary transitions , less funky roof lines and quasi insulated knee wall spaces etc,  will still result in a more efficient ouse that its easier to pass energy codes. It is unclear to me how HERS rating software will change to incorporate the increased specificity of building volumes and to ensure greater consistency among ratings.


Adin Maynard
Principal/Owner HIS & HERS Energy Efficiency 

2015 IECC and the 2017 Massachusetts Stretch Code

2015 IECC and the 2017 Massachusetts Stretch Code

The MA 2015 IECC is very similar to the current 2012 IECC. Blower door and duct leakage testing thresholds remain the same, prescriptive R-values are the same, continuous ventilation and high efficacy lighting are still required. If you have successfully built to the 2012 IECC, you are in good shape.

The new Stretch Code is a bigger jump that requires a robust HERS 55.

In Process - Arts Trust IR and enclosure design

The Northampton Arts Trust building project is a retrofit of a steel framed building originally built in the 1980s as a drive-through lumber yard. When complete, it will be a lively downtown space for the performance and visual arts. A primary goal of the project is a building with very low energy costs; after a large capital investment, the non-profit requires low operational expenses. Energy modeling is being completed to inform thermal enclosure design and to leverage utility rebates and incentives. 

The images below are from a basic infrared scan completed on Feb. 13, 2014. The insulation approach for the walls, roof, foundation walls, and slab are still being determined. The eQuest model will be completed soon to help assess the performance improvements of several enclosure system options. 

Existing Wall

  • Steel frame with 2x8 stud walls to the interior. Metal cladding is fastened directly to frame, there is no sheathing. &nbsp;'Bag 'n Sag' vinyl encased fiberglass was the original insulation strategy. Visual inspection shows this to be in decent condition with few rips. Estimate R-value (not accounting for wind-wash loses) &nbsp;R-2 - R-5
  • Very poor fiberglass batts were installed in the 2x8 stud cavities. IR images mostly convey the performance of this material.  R-2 - R-5 estimate thermal resistance value. 
  • There are significant connections through rim band areas to the basement. There are also major outside connections through exterior wall cladding above the drop-ceiling, the current very poorly defined 'boundary'.  Significant air leakage is compromising existing batt insulation. 

Existing Roof

  • Steel frame with 'bag and sag' was the original insulation strategy.  A drop ceiling was installed, about 4' below roof deck, with 6" fiberglass batts and mechanical equipment and distribution system in the cold attic space.  
  • Roof structure is an original metal (or fiberglass?) roof with a standing seam metal roof later installed. It is assumed there is sheathing and the appropriate membrane materials under the standing seam roof. 

Proposed wall

Remove existing metal panel cladding 4-6" of polyisocyanurate to exterior of existing wall. R-26- R-39

Optional: With frame of building exposed, remove existing fg batt, and 'bag and sag' insulation from exterior and insulate 2x8 framed cavities with mineral wool batts . R-24

Proposed Roof

Remove drop ceiling and remove existing standing seam roof and install 6"- 8" of polyisocyanurate on exterior of existing roof. Install sheathing, continuous WRB, air control membrane, and new standing seam roof.    R-39 - R-52

Optional - remove 'bag and sag' and install 3-4" of closed cell rigid foam to the interior of roof deck.


8 Strategies to Pass the 2012 IECC Code

8 Strategies to Pass the 2012 IECC Code

Builders and designers that specialize in energy efficient buildings will not have a problem with the shift to the 2012 IECC. Yet other builders may have some serious wake-up calls. Fortunately there are some proven strategies that will all but ensure compliance with the 2012 IECC and pending Stretch codes. 

In the spirit of ‘year in review’ countdowns, here are my....

8 strategies to surpass the 2012 IECC residential energy code 

Mass Save DER Guide - opens the market...very specifically

Mass Save DER Guide -  opens the market...very specifically

HIgh R-value mixed assemblies (including hot roofs!) spray foam, are now rebate-able through the Mass Save program-  without fixed prices - meaning the narrow utility perspective of 'cost effective' has moved aside for market realities and a competitive market. This is great news for humankind!

The Data Opportunity for Home Performance

The Data Opportunity for Home Performance

Impacting several buildings a year is great, but using technology to scale residential energy retrofits is what is drastically needed to solve our building energy crisis.  

Since utilities and implementation contractors aren’t exactly on the cutting-edge of innovation to streamline residential energy efficiency projects, why haven’t tech and building savvy start-ups jumped at the glaring opportunity to drive residential EE with data?

When an Energy Audit isn't an Energy Audit.

When an Energy Audit isn't an Energy Audit.

The utility provided assessments and amazing rebates and financing offerings serve many homeowners well. Yet for homeowners wanting to significantly change their homes- address ice damming, solve comfort issues, or achieve 25-50% energy savings- these services are not appropriate. A more detailed assessment approach is needed to identify improvements and communicate to the customer the value of investing in comprehensive solutions.