Written by Rafal Olan
The “Home Energy Rating System” (HERS) is a nationally recognized system for an analysis of a home’s energy efficiency. This includes protocols for inspecting a home, various testing methods, and all the calculations needed for a most accurate breakdown of house’s energy usage. The outcome of all these inputs into a computer software generates a HERS Index Score which is almost like a home’s ‘MPG’ sticker. The lower the score the less energy it uses.
The HERS Index Score compares your specific home to a ‘reference home’. To get a house’s index score, a certified Home Energy Rater has to conduct a Home Energy Rating and design the inspected home into computer programming. This encompasses all the construction details, the home’s shape, size, all the surface envelope areas and their insulation values, equipment efficiencies, and the testing results. This software compares these given specifications to the reference home of the same size and shape but minimum insulation values and equipment efficiencies. This reference home is an average newly built home to the 2006 IECC, International Energy Code Council, code minimums and is scored at a HERS Index of 100. An easy way of looking at it is that this minimum code compliant home will use a 100% of the energy, an average new house. The U.S. Department of Energy established that a typical resale home should be scoring about HERS Index of 130. Therefore, that average existing house will use about 130% of the energy compared to new construction, average reference home. You will also need to keep in mind that every older home is different and this HERS 130 is just an industry average. Same goes for the reference home, if you live in the 2009 IECC code jurisdiction, then your average newly code built home could be HERS scoring in the lower 90’s.
The HERS Index Score is a great tool for determining and comparing the true efficiencies of a house, either for new construction or for existing homes. In both scenarios, we can use the Index Score to see any differences in proposed efficiency upgrades to construction details. The better we can design and build a home the lower its energy usage will be. A house with A HERS Index of 60 will use only 60% of the energy compared to our standard, reference home, making it 40% more efficient. A score of 20 will use 20% or be 80% more efficient. And finally, if one builds a home with HERS Index score of ZERO, that house will generate all its energy needs on site and will not require any outside sources of purchasing energy. Along with the Index Score a host of different building reports are also generated from the Energy Rating and the energy modeling. From all those we can analyze the building in depth and see exactly where the home’s energy needs are. The HERS Index Score is the ‘MPG’ sticker and then some for our homes.