What
is the HERS Index?
The HERS Index is a scoring system established by the Residential
Energy Services Network (RESNET) in which a home built to the
specifications of the HERS Reference Home scores a HERS Index of
100. This index of 100 represents the energy use of an “
An index of zero indicates that the proposed building uses no net
purchased energy (a zero-energy home). An Energy Star® home should
have a HERS index of 85 or less.
In other words, the lower the HERS score, the lower the energy usage
of the home.
NOTE:
For every 1-point decrease in the HERS Index below 100, the Florida
Green Building (FGBC) Coalition provides 2 points toward the Energy
portion for a green home certification. For example, a HERS Index of
85 would provide 30 points on the FGBC checklist, reaching the
minimum required under the Energy category.
What Factors are considered for the HERS Rating?
There are a variety of energy-efficient features that have a
positive impact on the HERS Index including effective insulation,
high performance windows, tight construction and ducts, efficient
heating and cooling equipment, fluorescent or LED lighting, and
ENERGY STAR qualified appliances. The home does not have to include all of these items to reach
the required HERS Index of 85 or less.
What is the HERS Rating Process? A home energy rating involves an
analysis of a home’s construction plans and onsite inspections.
Based on the home’s plans, the Residential Energy Services Network
(RESNET)-certified Home Energy Rater uses an energy efficiency
software package to perform an energy analysis of the home’s design.
This analysis yields a projected, pre-construction HERS Index.
Upon completion of the plan review, the rater will work with the
builder to identify the energy efficiency improvements, if any,
needed to ensure the house will meet the ENERGY STAR performance
guidelines or other goals for the project. For example, by plugging
in various insulation or window options, this software can help the
builder decide what energy-saving features will provide the most
bang for the buck.
The rater then conducts onsite inspections and tests consisting of
the:
-
Blower door test
(to test the leakiness of the house)
-
Duct blaster test
(to test the leakiness of the ducts)
Results of these tests, along with input derived from the plan
review, are used to generate the final HERS Index score for the
home.
Is a HERS Rating necessary for an FGBC or NAHB Green Certification?
A HERS rating is not required for the FGBC green certification
process, however most projects find it difficult to achieve the
minimum points required in the Energy category without it.
A HERS rating will supply the necessary documentation to comply with
the Performance Path under the Energy-Efficiency category of the
NAHB Green Home Guidelines.
To view at a glance how the HERS Index along with the various tests play a role in the FGBC, NAHB and ENERGY STAR certification programs click here.
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