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HERS Ratings

A Home Energy Rating System (HERS) rating is a comprehensive assessment of the energy efficiency of a home expressed as a HERS Index.  HERS indexes can be calculated for single family homes, townhomes, duplexes, multifamily dwelling units, and sleeping units that utilize shared kitchens or bathrooms.  


A HERS Index of 100 indicates a home just meets the IECC 2006 energy code requirements, and each point above or below this index indicates a 1% increase or decrease in energy consumption.  For example, a home with a 130 HERS Index is projected to use 30% more energy, and a home with a 70 HERS Index is projected to use 30% less energy.  


A zero energy home (a home that produces enough renewable electricity over the year to cover all energy uses) would have a HERS Index of 0.


State energy codes provide pathways that utilize the HERS Index, usually referred to as an Energy Rating Index (ERI) in the code language. In Massachusetts, for example, all new residential buildings built in Stretch Energy Code municipalities are required to receive a HERS/ERI index of no more than 42-48 depending on their source of energy and other factors.


Utility incentive programs throughout New England also rely on HERS ratings for calculating energy savings and assigning incentive amounts for energy efficient construction.  This includes Mass Save, Energize Connecticut, Efficiency Vermont, NH Saves, and Efficiency Maine.

How can Airtight Energy Consulting support your project?

The HERS Raters at Airtight Energy Consulting, Inc. have extensive experience in guiding owners, developers, architects, and contractors throughout the HERS rating process. The typical steps in our process include:

  • Initial consulting on high performance building strategies

  • Preliminary HERS ratings and improvement analysis

  • Pre-construction training for trades

  • Foundation inspections

  • Insulation inspections

  • Final inspections including blower door testing


Airtight Energy Consulting can also provide certifications that build on the HERS index, including:

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