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

The 1550-square-foot prairie-style home with roughed-in basement is being built as a GreenMax Home under a program of Wisconsin Public Power Inc. Homeowners Tom and Verona Chambers collaborated with a home performance specialist and WPPI using computer modeling to help determine requirements. The home will use a PV system, a ground source heat pump for space conditioning and improved wall construction and insulation. The Chambers are committed to efficient use of energy and reduced their plan for a north side wall of glass by 40 percent. They will work with WPPI to monitor their energy use. Kurt Pulvermacher, energy service representative for WPPI, says paying special attention to overall building practices, including wall details, was key in the design of the home. "The Chambers concentrated on reducing the overall energy load in the home by focusing on an advanced wall-framing system that accounts Homeowners Tom and Verona Chambers have designed and are constructing the first net-zero energy home in the Upper Great Lakes region. for both better insulation and air sealing. In addition, basements in typical Wisconsin homes are big energy losers so they concentrated on reducing energy losses with an improved insulation package there as well." The design phase also included ways the Chambers could reduce their non-space conditioning loads, including the installation and use of all Energy Star appliances. Pulvermacher expects that the home's blower door test at CFM50 will show less than 500, compared to a typical home's 1,800. The photovoltaic panels, capable of producing 5.7kw in an hour of optimum sunlight, are on a base that can track the Sun across the sky. A tracking system typically provides 30 percent more production than would a stationary set-up. The system, as well as the energy-efficiency upgrades, will cost about $90,000. Federal tax credits, the state Focus on Energy public benefits program’s incentives and a $50,000 WPPI grant will bring the cost down to $23,000 for the homeowners. “It’s coming down to economics,” says Pulvermacher. Once the home is completed, its energy production and use can be monitored through updates on the WPPI GreenMax Home Web site. Costs and Attitudes As the concept of zero-energy homes makes its way into the marketplace, two factors play big roles: cost and consumer attitude. Costs. It can be cost-effective to reduce the energy usage in a home by up to 50 percent through air sealing, insulation, proper appliances and such. But adding the renewable energy sources that can get a home to net-zero energy usage can be expensive upfront. Having incentives at the local, county, state and federal levels does have an impact. Consumers in many areas enjoy credits, grants and rebates that can help them pay up to 50 percent of the costs of installation. However, incentives are not uniform across the country. Some areas have few or no incentives, making the renewable idea seem cost-prohibitive. Simple payback calculations can dominate thinking, says NREL’s Norton. “There’s a whole series of benefits not included in the cost: efficiency features, improved durability and comfort of the home, and societal benefits,” he says. “It also should be looked at as a good hedging strategy, hedging set rates against utility rates that could be a lot higher in 20 years.” Attitude. Consumer attitude is important in the move to ZEH. According to Lew W. Pratsch, project manager with the DOE’s Building America program, research discovered that optional ZEH was the hardest to sell. However, pre-plotted subdivisions with from 10 to 30 percent ZEH homes sold as fast as other homes, and full ZEH subdivisions in the West sold faster than nearby conventional subdivisions. DOE surveys also found that homebuyers do not seek ZEH but like it—and brag about it—once they have it. Having an energy conservation state of mind also plays a role. While designers can plan for most requirements for a zero-energy home, the one thing they can’t account for is how the occupants will behave. In one home designed to be net-zero energy, the occupants ended up adding many non-Energy Star recessed lights and did not use the programmable thermostat or other energy-saving devices—effectively negating many of the enhancements. Bill Asdal says consumer behavior is tops in the bucket of solutions. “There is plenty to do without ever picking up a hammer, from seasonal window usage to appliance operation to filter cleaning and more.” NREL’s Norton says the tricky part in designing a ZEH is to account for the very variable plug load. Called MELs, miscellaneous electric loads, they are the occupants’ big screen TV, hair dryer and such. “In a ZEH, the home and the occupants make or miss the target together.” Read other Green Homes Special Series articles here.

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