Measuring Whole-Home Energy Efficiency
More and more builders are touting their homes' HERS Index as a way to standardize energy-efficiency claims.
In the alphabet soup world of construction shorthand, one acronym is popping up more often these days: HERS, as in the HERS Index.
HERS stands for Home Energy Rating System. It is a scoring system established by the Residential Energy Services Network (RESNET), an offshoot of the National Association of State Energy Officials and Energy Rated Homes of America.
Here's how the rating works: 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-percent reduction in energy consumption compared to the HERS Reference Home. That means, for example, that a home with a HERS Index of 85 is 15 percent more energy efficient than the HERS Reference Home; a home with a HERS Index of 80 is 20 percent more energy efficient.
Just as an appliance comes with a yellow sticker that estimates the amount of energy use, a number of well-known production builders are planning to use the HERS Index as the standard for an easy-to-reference label that describes a home's energy performance. Several national production buildersAshton Woods Homes, KB Homes, and the Pulte Group, which includes Centex Homes, Del Webb Communities, and Pulte Homeshave entered into an agreement with RESNET to release such home energy labels later this year. Ryland Homes, the country's ninth largest homebuilder, has also committed to having all of its homes energy rated and will market the HERS Index of these new homes.
The ability to measure energy efficiency at a whole-home level is also at the core of the Propane Energy Pod, which proposes to treat a home's top five areas of energy usespace heating, water heating, cooking, fireplaces, and clothes dryingas parts of an integrated system. But in addition to energy use, the Propane Energy Pod also establishes a model for measuring a home's annual carbon emissionsa growing concern for green builders and home buyers. Taken together, the Propane Energy Pod represents the logical next step in the progress toward the establishment of deliberate practices for the reduction of energy use and carbon emissions by new homes.