How Many Miles per Gallon Does this House Get?
Mountain Energy Consultants
By Chad Feagler
As the home is decompressed during a blower door test, air leaks in the window are revealed. ©sunshine divis photography
Although energy efficiency information for the greatest sources of home energy consumption-heating and cooling equipment, water heaters and other home appliances-is provided on the product label, no such label comes stamped to the side of the house itself. A home energy rating, comparable to checking the miles per gallon sticker on a new car, fills this need.
Although home energy raters come from all walks of life, they typically come from the building or energy industries. All home energy raters are certified by RESNET (Residential Energy Services Network), complete a rigorous education and testing process and abide by RESNET's standards of practice and code of ethics.
Index Graphic: The HERS Index is a registered trademark of the Residential Energy Services Network, Inc. and can not be used without written permission. Trade marked 2007. All rights reserved.
A home energy rating incorporates the Home Energy Rating System index score (HERS). The HERS index score provides a standard measurement of a home's energy efficiency and expected energy costs for both new and existing homes. The index score runs on a scale from zero to over a hundred. The score of 100 has been assigned to the HERS reference home which is based on the 2004 International Energy Conservation Code. A one-point decrease in the index is equal to a 1% reduction in energy consumption. If a home scores an 80 in the index it is 20% more efficient than a home built to the 2004 IECC “American Standard Home.” A score of zero indicates that the home uses no net purchased energy. The lower the HERS index score, the better.
The HERS index score is produced by the rater through a review of the home. The rater will conduct an on-site visit, and inspect all aspects of the home affecting energy consumption. The rater will gather technical information such as window efficiency, insulation levels, solar orientation, and heating and cooling equipment efficiency. Diagnostic testing includes a blower door test and duct blasting. A blower door test uses a fan to depressurize (force air out of) the home. Depressurization reveals hidden air leakage sites in the building shell. A blower door test is extremely important in gauging energy usage as air leakage can increase heating and cooling cost over 30% and cause moisture and comfort problems. If duct work is used for distributing conditioned air, a duct blaster will accurately measure the air leakage from the duct work. The rater will then take all the information gathered on site and enter it in accredited RESNET software to produce the HERS index score.
The HERS index score allows for comparison between one home's energy efficiency and another, and is also used for qualifying homes for Energy Star Homes (a score of 80 on the index is needed in Routt County), Built Green Colorado, LEED for homes, Builder's Tax credits, city/county green building programs, and energy efficient mortgages.
Green building has reached mainstream status. Banks are now more likely to issue loans for green homes as they view them as a sound investment. More builders understand that rising energy costs are an incentive to build green. Real estate brokers around the country are becoming Eco-Brokers and have learned the marketing power of green homes. Energy efficiency is the foundation for green building. A home energy rating is your first step in going green. 
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