Page 61 - Green Builder July-August 2017 Issue

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CODE ARENA

The Latest Rules, Regulations and Codes Impacting Sustainable Construction

Stepping up the HERS Index

A positive aid to the homebuilding industry could be even better with a few upgrades.

BY MIKE COLLIGNON
Note: The following article is based on a presentation given at do using the HERS/ERI path.”
■ Mass walls. The HERS/ERI does not model thermal mass
the 2017 RESNET Conference by Robby Schwarz, principal and effectively, especially when combined with insulation, like we see
■
director of Builder Relations at EnergyLogic.
with most insulated concrete wall systems. While it relates to the
HE HERS INDEX has been a positive addition to the previous bullet, it can also be problematic for custom home builders
homebuilding industry, on a number of levels. It enables who are simply using these high-performing wall systems to more
a builder to baseline the efficiency of their product. It easily provide their clients with code-compliant homes.
has introduced additional flexibility to the energy code ■ ■ Ventilation. Building tight and ventilating right is a basic
T through the Energy Rating Index (ERI) pathway that is building science principle. The difference between supply, exhaust
largely based on the HERS Index and was originally adopted into and balanced ventilation is not adequately accounted for in the
the 2015 International Energy Conservation Code (IECC). current modeling software.
From that, builder resistance to energy code adoption has decreased These are just a few suggestions. However, we appear to be at a
(though to what degree depends on the jurisdiction and the IECC crossroads. We want a system that not only quantifies the efficiency
edition that was adopted). It has also increased design and product of a home, but also develops a true energy model that can answer
choice freedom. It has brought the building and energy efficiency complex questions about the performance of the entire home as
communities together to debate the degree of energy efficiency, well as the components that built it. The HERS/ERI path is not that
instead of whether we should incorporate it at all. But perhaps system. Going forward, the industry may need to make a decision
most importantly, it has created a simple metric and corresponding to either only use the HERS/ERI path as it was intended (to create
marketing message that the homebuying public can understand, an Index score) or to significantly enhance the system to be able to
regardless of its ability to comprehend building science. adequately answer other in-depth performance questions we have
Yet, like most computer models, it is under constant scrutiny and about our homes.
refinement. This is logical, since the homebuilding industry does There will always be ways to improve modeling programs, and
not remain static. We want/need innovation in our construction we should always strive for ways to improve them. The day we stop
products and techniques. Therefore, our modeling programs need to offering suggestions is the day people stop caring, and that is far
accommodate those advancements. The following items are aspects worse for our industry. GB
of the program that could use some additional refinement:
■ Energy optimization. Many builders are looking for the HERS/ Mike Collignon is the executive director and co-founder of the Green
■
ERI path to help them optimize their specification. “The simple fact Builder Coalition.
is that the system cannot and should not be used to allocate a dollar
per Index point,” said Schwarz. The system is not linear because it COURTESY OF
uses a systems approach and analyzes the synergies between all

components used to build the house. One upgrade will not always The Green Builder Coalition
give you a specific number of Index points. The Green BuilderCoalition is a not-for-profit association

■ Very high-performing homes. It’s difficult to get below a HERS
■
40 with a super-insulated home with a state-of-the-art mechanical dedicated to amplifying the voice of green builders
system. Although there may be energy benefits, the HERS/ERI path and professionals, driving advocacy and education for
stops allocating Index points due to diminishing returns. This poses a more sustainable homebuilding practices.
problem for builders and designers of high-performance homes such For more information, visit GreenBuilderCoalition.org
as passive homes, which are gaining market share. “For example, if
you’re designing a passive house, it is important to be able to rely on For more information, contact Executive Director Mike Collignon
energy modeling software to guide you to the right solutions,” said at mcollignon@greenbuildercoalition.org.
Schwarz. “Currently, that’s not something designers can confidently

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