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Innovative home produces as much energy as it uses

The Ultimate Family Home, built by Pardee Homes in partnership with NREL and ConSol, Inc. energy consultants, combines an 8-kW photovoltaic array and energy-saving measures that use 90 percent less energy than a conventional home to produce as much energy as it consumes. (Photo courtesy of National Renewable Energy Laboratory)

Zero, a number representing nothing, represented big energy savings when the National Renewable Energy Laboratory and its partners, Pardee Homes and ConSol, Inc., unveiled the Zero-Energy Home at the 2004 International Builders' Show in Las Vegas.

By combining renewable energy technologies with highly energy-efficient construction, the home produces about as much energy as it consumes annually to achieve “net zero” energy consumption. The Ultimate Family Home, as Pardee calls it, was the result of a DOE initiative to bring the latest research in energy efficiency and renewable energy to the building industry. “We want to make people aware that the technology for homes to produce their own energy exists now, that it’s not something that is off in the future,” said NREL Zero Energy Homes Program Manager Tim Merrigan.

Comfort and efficiency earn ZEH house show home status
Pardee built the 5,300-square-foot custom home at the Nevada Trails master-planned community. An 8-kW, rooftop photovoltaic array provides electricity, and a solar hot water system heats the home’s water. Good insulation, air sealing and advanced windows work with a highly efficient air-conditioning system to keep the house comfortable, and energy-efficient appliances add to the savings. The home uses about 90 percent less energy than a similar home built strictly to code.

ZEH homes use three basic strategies to dramatically reduce the amount of energy a single-family home consumes.

  • Tight shells. Extra insulation in the walls, floors and ceilings; strategic window placement and smart windows that limit solar heat gain; and reflective, radiant barrier roofing.
  • Energy efficient heating and cooling systems including tankless water heaters and state-of-the-art heat pumps, and major appliances that exceed Energy Star-rated efficiency levels.
  • A cost- and pollution-free energy source. Wind power, fuel cells and biomass generators are alternatives, but currently, all ZEH homes use state-of-the-art PV systems.

As any real estate agent knows, however, practical considerations alone do not sell a home. Pardee held focus groups to learn what families want and need in homes, and shared that information with Bassenian/Lagoni Architects, designer of the Ultimate Family Home. “The house had custom touches like a heated workshop and surround sound for men, a workspace nook in the kitchen, even a secret room in the girl’s bedroom to hide from her little brother,” Merrigan said.

That attention to the market paid off when the National Association of Home Builders selected the house to serve as a show home for the builders’ convention. “It showed that energy efficiency and solar energy could be incorporated into attractive homes that come with everything homebuyers are looking for,” stated Merrigan.

Sunbelt states embrace ZEH concept
As energy prices rise and concerns about the security of the nation’s energy supply push the development of affordable renewable energy, builders are seeing an opportunity in ZEH technology.
Clarum Homes and Morrison Homes, two more homebuilders NREL partnered with for the ZEH initiative, are building developments in Watsonville, and Elk Grove, Calif., respectively. The Armory Park del Sol neighborhood in Tucson, Ariz., is being built by John Wesley Miller Companies in cooperation with NAHB Research Center.

Sacramento-area homebuilder Premier Homes is working with ConSol on a 95-house subdivision, and has received additional subsidies from the Sacramento Municipal Utility District. SMUD is providing the builder $200 per home for advanced energy-efficiency features and about $7,000 per home toward the cost of each 2-kilowatt solar tile rooftop system. The utility will also offer $20,000 to help market the homes.

SMUD's maximum total contribution is more than $700,000, about half of which is coming from the money remaining in the 2003 Public Good fund. The other half is part of the 2004 budget.

In addition to the incentive program, SMUD is assisting NREL by collecting data on ZEH homes in its service area.

Cost of energy savings
Most of the ZEH houses under construction are competitively priced with conventional homes. The energy-thrifty homes in the Premier Gardens subdivision are intended for entry-level homebuyers, the people who most need the energy savings. Some of those homebuyers may qualify for energy-efficiency mortgages, which subtract projected energy-cost savings from projected expenses to help defray the initial costs of adding the energy-efficient features.

The PV system and energy efficiency features add $8,000 to $16,000 to the cost of a ZEH house, mostly in up-front training and retooling costs, said Rob Hammon, ConSol’s chief consultant on ZEHs. Once those expenses have been covered, mass production helps stabilize the cost. Over the long haul, he added, the homes can actually be cheaper. “The increased cost of the home is cut down by the energy cost savings,” Hammon explained. “It's possible for the homeowner to get right to the break-even point.”

Or, as one Clarum Homes representative put it, “The electric meters spin backwards.”

Her comment highlights the fact that so far, all ZEH developments are in net-metered states. In net-metering situations, the homes are connected to the utility grid. The homeowner can sell extra electricity to the utility, which offsets electricity purchased at other times, such as at night.

Obviously, noted Merrigan, it would work differently in states where consumers cannot sell energy back to utilities. “It might mean a smaller PV array that wouldn’t produce any more energy than the home would use,” he said. “One of the points the initiative is trying to make is that you don’t have to take a home all the way to net-zero consumption to still take a big chunk out of your energy bill.”

NREL is working to get more utilities involved in the ZEH initiative, since more builders are looking to add super-efficient and energy-producing models to their stock. Pardee plans to incorporate many of the technologies used in the Ultimate Family Home into some of its new-home neighborhoods this year, while Clarum is planning more ZEH developments. Premier sees building solar-powered, environmentally friendly homes as a way to set the company apart from its competition. If the market continues to demand more energy efficiency, as these companies believe, nothing is about to turn into something big.