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Tucson Zero Energy Home Sets the Stage for Further Research

The Tucson Zero Energy Home, which was designed to generate as much energy as it consumes, was sold less than one month after its grand opening earlier this year.

The 1,718 square-foot home, which was built by Tucson builder John Wesley Miller in partnership with the NAHB Research Center and Tucson Electric Power, is part of a national demonstration program that is introducing the concept of the zero-energy home into the single-family home building industry.

The program is funded by the U.S. Department of Energy through the National Renewable Energy Lab.

Built in Miller’s Armory Park del Sol community — a downtown Tucson subdivision that features energy efficient design and renewable energy systems — the home is connected to the utility grid but it has been built with features that reduce its need for energy and take advantage of electricity generated by the sun.

Tucson Electric Power has agreed to run the home’s meter backward and credit its owners when the home’s renewable energy systems put power back into the grid.

Reducing the home’s cooling load — a major objective of its desert-climate design — has been achieved through the use of thermal mass walls with increased exterior wall insulation, low solar heat gain windows, porches for window shading, radiant barrier roof decking and reflective roof coating.

To reach the goal of zero net-energy use, the home combines an efficient building design, very high-efficiency air cooling equipment, a solar thermal space and water heating system, high-energy lighting and appliances and a 3.5 kilowatt photovoltaic array.

Special attention was also given to lighting and appliance loads, which are higher than the combined heating and cooling loads in the home’s design.

Using energy simulation software, the design team studied 32 combinations of energy features.

The final package they decided upon includes: two-inch polyisocyanurate wall insulation, R-43 ceiling insulation, an 18-SEER air conditioner, a solar thermal space and water heating system, Energy-Star-rated appliances and a permanent fluorescent lighting package.

Engineers made their choices based on the lowest life-cycle and upfront costs.

Other energy saving features of the home include: radiant barrier roof decking, reflective roof coating, a tankless water heater with a plastic PEX hot water distribution system, water-saving bath and kitchen fixtures, placement of ductwork in conditioned space, clustering of hot-water fixtures where possible, compact house design, efficient ventilation fans and a programmable thermostat.

NAHB Research Center engineers will be monitoring the home’s performance for the next year.

The following companies sponsored the project: BP Solar; Carrier Corporation; Dankoff Solar; Global Solar; Kohler Co.; Microtherm, Inc./SEISCO; Milgard Windows; Nora Lighting; Osram Sylvania; Panasonic; Panasonic Ventilation; Sioux Chief Manufacturing Company, Inc.; SMA America, Inc.; SunEarth, Inc.; Sun Lighting of Tucson; Studor, Inc.; LP Corporation/TechShield; The Solar Store; and Whirlpool Corporation.

For the next phase of its research in this area, the NHB Research Center is now looking for participants who construct more than 100 homes per year to build zero energy demonstration homes across the country and in various climates.

Eventually, entire neighborhoods of these homes will be built.

Builders, manufacturers, utilities, lenders, Realtors®, appraisers and others who are interested in participating in future projects can e-mail Jeannie Leggett Sikora or call her at 301-430-6289.

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