W h a t  i s  a  H E R S  R a t i n g ?

A home energy rating involves an analysis of a home’s construction plans and onsite inspections. Based on the
home’s plans, the 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 needed to ensure the house
will meet ENERGY STAR performance guidelines. The rater then conducts onsite inspections, typically including
a blower door test (to test the leakiness of the house) and a duct test (to test the leakiness of the ducts). Results of
these tests, along with inputs derived from the plan review, are used to generate the HERS Index score for the home.

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 (based on the 2006 International Energy Conservation
Code) scores a HERS Index of 100, while a net zero energy home scores a HERS Index of 0. The lower a
home’s HERS Index, the more energy efficient it is in comparison to the HERS Reference Home.
Each 1-point decrease in the HERS Index corresponds to a 1% reduction in energy consumption compared to the
HERS Reference Home. Thus a home with a HERS Index of 85 is 15% more energy efficient than the HERS Reference
Home and a home with a HERS Index of 80 is 20% more energy efficient.
For more information, visit http://www.natresnet.org/
Comparing the New HERS Index with the Old HERS Score

For homes rated before July 1, 2006, the rating score is known as a “HERS Score.” The HERS Score is a system in
which a home built to the specifications of the HERS Reference Home (based on the 1993 Model Energy Code) has
a HERS Score of 80. Unlike the HERS Index, each 1-point increase in a HERS Score is equivalent to a 5% increase
in energy efficiency. Please see the table below for a comparison of the HERS Score and the HERS Index.

HERS Score HERS Index

Reference Home Score Reference Home is assigned a HERS Score of 80 Reference Home is assigned a HERS Index
of 100, while a net zero energy home is assigned a HERS Index of 0
Reference Home Basis 1993 Model Energy Code (MEC) 2006 International Energy Conservation Code (IECC)
Scale Each 5% increase in energy efficiency corresponds to a 1-point increase in HERS Score Each 1% increase in
energy efficiency corresponds to a 1-point decrease in HERS Index
Energy Use Considered Heating, cooling, and water heating Heating, cooling, water heating, lighting, appliances,
and onsite power generation*
ENERGY STAR Requirement HERS Score 86 HERS Index of 85 in climate zones 1–5
HERS Index of 80 in climate zones 6–8
Status Phasing out Approved by the RESNET Board of Directors. To be implemented as of July 1, 2006.
* Note that although onsite power generation is included in the RESNET HERS Index, it cannot be used to decrease
a HERS Index to qualify for ENERGY STAR.

For more info on green homes and green real estate in Durango please call or email us. We got some exciting new green projects in Durango, some solar and even a few zero energy homes.

Claudia Williams 970 749 3555