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         Photos 1, 3, & 9 courtesy Eco Futures; all others by Ty Wyant. |
Home&Garden feature article
How does a monthly $5 energy bill sound? For one Boulder family, it’s a pleasant reality. By Shannon Burgert
Why so low? Because Solar Harvest, the city of Boulder’s first zero-energy home, exploits Colorado’s sunshine through a solar sun space and solar-electric roof panels. In fact, the city’s chief building official approved the home without a fossil-fueled backup heating system—an atypical move. “This house asks, ‘How far can we go with solar?’” says Doub, president of Ecofutures Building Inc., a local company that constructs energy-efficient, high-performance homes. Doub projects solar power can meet all of Solar Harvest’s energy needs, and then some. In fact, his home’s 6.8-kilowatt photovoltaic (PV) system will prob-ably generate more electricity than his family can use, enabling him to sell the excess to Xcel Energy through an agreement called net-metering. The home’s projected $5 to $10 energy bill covers connection charges and natural gas for the range and dryer, but that expense should be offset by the surplus sold to Xcel. Solar Harvest’s eye appeal wasn’t sacrificed for energy efficiency, either. Childs designed the interior, which is clean, contemporary and inviting, even though it features many salvaged and recycled ma-terials. “I wanted to create a sophisticated and intriguing, yet warm, family-functional environment that showcases natural light, color and texture,” Childs says. She also wanted special spaces for both adults and her children. The home’s floor plan accomplishes that through a basement climbing wall for Ariel, 8, and Brian, 6, and brightly colored top-floor bedrooms where the kids can romp with pets. here comes the sun A 275-square-foot sun space on the main floor’s south side should meet most of Solar Harvest’s heating demands. Warm air from the sun space is circulated through the house by fans and ducts, and the heat is readily retained by double Sheetrock insulation. Even when outside temperatures fall to 2&Mac251; F while the sun is shining, the sun space will still meet 125 percent of the home’s heating needs, Doub predicts. In summer, when the sun is high in the sky, an overhang prevents sunlight from entering the passive-solar sun space, which acts as a greenhouse in winter. If the sun space does overheat, a heat-rejection fan can be turned on. A solar water tank provides supplemental heat. Twelve salvaged solar-thermal collectors on the roof heat water for space heating, faucets and the hot tub in a 6,000-gallon, super-insulated cistern. Hot water is supplied to the home through coiled tubes immersed in the tank. When fully “charged” at 190&Mac251; F the water tank can heat the house to 68&Mac251; F through eight consecutive, 2&Mac251; F, cloudy days. Such weather conditions are rare in Boulder, hence the home’s unusual approval for no fossil-fueled backup heating system. While the sun warms Solar Harvest in winter, a ground-source cooling system cools it in summer. Precooled fresh air enters the house through pipes buried 6 to 8 feet underground, where the ground temperature remains at 55&Mac251; F. The system also pre-warms air during colder months. At night, a whole-house fan exhausts hot air, which can also escape through an adjustable skylight. The double Sheetrock insulation also helps maintain a cool house. An Energy Recovery Ventilation system draws in fresh air and vents stale air to the outdoors through a series of pipes. The system allows for 96-percent heat recovery, as exhausted stale air crosses paths with incoming fresh air. Solar Harvest’s windows are another exciting energy-efficient feature, Doub says. Even windows with a high insulation value lose heat through their frames, he notes. But Solar Harvest’s windows are so well insulated that on a 0&Mac251; F day with a 15 mph wind the windows’ interior surface temperature will remain at 65&Mac251; F. cash out, cash in Doub says the extra expense to build his zero-energy home was $60,000 to $70,000, which includes the discounted, $41,000 PV system (retail cost is $54,000) before a 50-percent tax rebate; $12,000 to $15,000 for the solar water tank and heat exchangers; $14,000 for extra insulation; and an additional $10,000 for windows. Based on today’s energy costs, he projects the PV system will net $57,000 of profit from extra energy generated over the next 25 years. When he gets his first check from Xcel, “I’m going to frame a color copy, then cash it,” he says with a grin. While a net-zero energy bill is certainly appealing, Craig Christensen, a researcher at the National Renewable Energy Laboratory’s Center for Buildings and Thermal Systems, cautions that zero-energy homes are expensive to build and fluctuating energy prices mean unpredictable savings. “Savings are high today because of the current price of natural gas,” he says, but there’s no way to forecast future energy prices—or potential savings. Christensen also owns a super-insulated, passive-solar home. “I haven’t regretted it for a day as an experiment and as the socially responsible thing to do,” he says, though he’s sat through 20 years of low energy prices. But given today’s energy prices, “now I can really appreciate having affordable utility bills,” he says. While Doub touts the energy savings he expects to reap from his solar home, the “payback” is harder to calculate, even with predictable energy bills. Still, he’s frequently asked to put a value on his savings. “People put $50,000 into a car and they don’t ask about the payback,” Doub says. “That car is losing money every day.” Currently, only five homes of Xcel Energy’s 1.5-million Colorado customers have reached net-zero energy status. But Doub believes there’s no better place to store his money than in his home. Solar Harvest crowns Doub’s 24 years of work in the energy-efficient, high-performance housing industry, and he hopes his home sparks a trend. “I imagine the day when ReSource will have PV panels lined up, just like it has doors,” he says, referring to a Boulder-based business that sells salvaged building materials. As for energy, Doub says it’s hard to pinpoint the true price, as fossil fuel’s hidden costs don’t appear on any energy bill. “What are the energy costs in terms of healthcare, the environment and the climate?” he asks. A valid question that deserves an honest answer. Shannon Burgert is a freelance writer who teaches biology at the University of Colorado and gifted-and-talented classes at Superior Elementary School. She focused on energy-efficient buildings as a former science writer for the National Renewable Energy Laboratory in Golden.
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