Green Homes Special Series: Part Fourteen: Zero-Energy Homes

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Zero-energy homes, or ZEHs, were just a great idea several years ago. But with research and incentives, they are gradually becoming a reality in several parts of the country. Asdal Companies produced the country’s first net-zero remodeling project with its transformation of this Civil War-era cottage in New Jersey. Netting Zero Energy According to the U.S. Department of Energy (DOE), ZEHs have “the potential to reverse national upward trends in home energy consumption for the entire U.S. housing stock.” A net-zero energy home is designed to produce as much energy as it consumes in a year. That is accomplished by creating a home that is well-designed, well-sealed and insulated, and uses on-site renewable energy such as photovoltaic panels and solar water heating. It is connected to the grid and may use more energy than it produces on some days but “nets” zero over a year. “There are zero-energy homes, custom and production built, that work and are being lived in,” says Paul Norton, senior engineer with the National Renewable Energy Laboratory in Golden, Colo. “Can we build every house that way? Not yet, but codes are moving that way. You could say we have gone beyond the advanced prototype phase into the early market introduction.” Asdal Companies produced the country’s first net-zero remodeling project that started with this rough-looking Civil War-era cottage. Levels of Efficiency The National Association of Home Builders (NAHB) Research Center in Upper Marlboro, Md.; the National Renewable Energy Laboratory and the U.S. Department of Energy’s public/private collaboration known as Building America are developing energy solutions for new and existing homes. There are already Energy Star homes that are at least 15 percent more energy-efficient than homes built to the 2004 International Residential Code. In February 2008, the DOE announced a Builders Challenge to have homes built to new efficiency measures based on Building America’s high performance home strategies. Those homes would have to measure at least 70 on an EnergySmart Home Scale, or E-Scale. The E-Scale rating for a home is determined after the home is performance-checked using the Home Energy Rating System (HERS) Index, developed by the Residential Energy Services Network. The E-Scale provides a context to determine relative efficiency of homes in a region. A typical home built to code would be 100 on the scale. An Energy Star home would be 85, meaning that home would use 15 percent less, or 85 percent, of the energy of a typical home. A Builders Challenge home, at 70 or less, would be that much more efficient. The zero-energy home, at zero, would be the best. The Builders Challenge threshold of 70 on the E-Scale is expected to stay at that level until 2012. As greater efficiency levels become available, the Challenge threshold would edge closer to zero. The DOE expects that by 2030, builders will have the methods and technologies to cost-effectively construct net-zero energy homes anywhere in the United States. The challenge is to get to “cost neutral,” where the added first costs of system enhancements amortized over 30 years would equal monthly energy cost savings from the enhancements. Projects and Outcomes Here’s a quick look at some zero-energy home projects around the country and the lessons learned from each home. Two-story colonial in Maryland Bob Ward Companies, one of the largest homebuilders in metro Baltimore, Md., Bob Ward Companies offers consumers the option of an ultra-efficient home with its MEG, Maximum Efficiency Greenland, series. teamed up with the National Association of Home Builders Research Center to develop a zero-energy home as a training and educational endeavor. The 2,566-square-foot two-story colonial with a full basement and attached garage was constructed in 2005. Purchasing Manager Joe Gregory says that trying to get to a net-zero home takes time, effort and money. While the demonstration home only got to 80 percent of the net-zero goal, it did go far beyond efficiencies typically offered. The company now offers homes to an ultra-efficient level that, minus the solar electric, save 13,934 kwh a year beyond typical construction in that region. “Adding solar electric and solar hot water has a lot to do with where the home is being built,” says Gregory. “Some states have residential incentives available. For somebody to try to do it around here, it’s out of reach for the average home buyer.”

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