Creating a Zero-Energy Home

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Bringing a home to zero energy use requires changes in lifestyle, energy production, and monitoring. A zero-energy home (ZEH) produces as much energy as it consumes over a year's time. The only way to achieve this is through energy-efficient design and practices coupled with energy-producing technologies. Reducing Energy Demands In addition to a lifestyle committed to energy conservation, building a zero energy home requires energy-conscious design and technology. "There can be no compromise on anything," says Danny Parker, Principal Research Scientist for the Florida Solar Energy Center. How the house is oriented and designed are as important as the photovoltaic panels used to generate energy. Reducing the energy demands of a home is the most important first step in creating a ZEH. "The question to be asked is: 'How do I reduce the loads in the building to be as minimal as possible?'" Parker says. The answer will vary regionally, as the nature of those energy demands depends largely on climate. A home in Minnesota will face significant heating demands, while one in Florida will consume most of its energy cooling the house. "You need to pull out all the regional tricks," Parker says. To that end, designing and implementing an energy-efficient HVAC system can reduce energy loads by as much as 80 percent. For a home in Florida, using light-colored roofing tiles and spectrally selective windows will reduce the heat load of the building, which in turn reduces the demands of the cooling system. Internally, Energy-Star rated refrigerators, washers, dryers, and other appliances will also lower the energy required in the home. Producing Energy for the Home When a home is designed, built, or retrofitted to be as energy-efficient as possible, the second step is to employ energy-producing technologies—starting with the sun. Solar thermal technology uses the sun to heat material that is then stored thermally for later use. This technology includes hot water systems. Solar thermal systems are cost-effective solar solutions and are priced far less than their photovoltaic (PV) counterparts. "Solar thermal doesn't get into the 4 or 5 digits in cost, like PV can," says Tim Merrigan, senior program manager at the National Renewable Energy Laboratory. Once a home is energy-efficient and set up with solar-thermal water and heat collection, PV technology adds the electricity-producing component that helps bring the energy tally to zero. PV technology harnesses the power of the sun to generate electricity that is collected as direct current (DC) and either sent to

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