Tennessee Valley Authority has taken a straightforward approach to comparative analysis of home performance: build a few houses that have similar layouts and interior space, but use different construction techniques and materials to see which combinations work best.
So far, a total of 15 homes, including three nearing completion, have been designed and built by TVA and various partners, including Oak Ridge National Laboratory, to test various construction, material-use, and energy-management strategies pegged to both cost and performance. These projects include a series of Habitat for Humanity homes built with structural-insulated-panel shells in Lenoir, Tennessee, and four 2,800-sq.-ft. homes in the Wolf Creek subdivision in Oak Ridge, Tennessee, designed for net-zero-energy performance as part of a research project called the Zero Energy Research Building Alliance, or ZEBRAlliance.
The three homes approaching completion are part of yet a third endeavor, called the Campbell Creek research project, whose partners include ORNL and the Electric Power Research Institute. The houses have similar layouts and are in the same Knoxville-area neighborhood, but feature different approaches to construction and energy efficiency management.
An (almost) living lab
With the three homes unoccupied but operating – a robotic system in each turns lights on and off, opens and closes the refrigerator door, and otherwise simulates occupant utility use – the Campbell Creek project essentially will be a three-year lab experiment designed to monitor the effectiveness of new-construction and retrofit techniques, materials, and monitoring systems in light of a controlled set of occupant behaviors. The ultimate aim is to determine which combination of factors yields the best energy efficiency in the most cost-effective way, and then use the information to educate builders, developers, and consumers about “demand response” – the approaches consumers can take to reduce energy use during peak-demand periods.
The eventual sale price of the homes is estimated at $250,000 apiece, TVA says, which includes about $30,000 each for upgrades and provisions to simulate occupancy and monitor performance. Manufacturers and suppliers contributed approximately $54,000 in materials, equipment and labor.
An energy efficiency progression
TVA describes the three homes as follows:
– One is a control home, incorporating local building codes, that represents a typical house currently built in the Tennessee Valley. In includes two SEER 13 heat pumps (4.5 tons total). TVA says the house is expected to use slightly less energy than a new house built to the International Energy Conservation Code. Interior conditioned space is about 2,400 sq. ft. Both this and the second home are built with R-13 walls and R-30 roofs.
– The second home was also built to local code, but was then retrofitted with energy efficiency technologies that an existing homeowner could add to improve efficiency, including a DuPont weatherization system, spray foam and fiberglass insulation in the attic, whole-house air tightening, a programmable thermostat, fluorescent lighting, Energy Star appliances, and a three-ton SEER 16 heat pump. This second home, also with about 2,400 sq. ft. of interior space, is projected to use two-thirds of the energy of a comparably sized new house built to code.
– The third home, with 2,512 sq. ft. of interior space, has been built to perform to near net zero energy, with airtight construction; R-22 walls and an R-49 roof; a two-ton SEER 16 heat pump; heat recovery from gray water, the dryer vent, and dishwasher; a programmable thermostat; triple-glazed windows; fluorescent lighting and Energy Star appliances; a rooftop solar power system; and a drainback solar hot-water system. TVA says this house is expected to use about a third of the energy required by a house built to code.
Says TVA: “In building these three houses, TVA has created a multimillion-dollar research facility for about 10 percent of the cost of creating the testing capacity in a laboratory.… TVA has not had a residential research project of this type underway since its solar home research in the 1980s.”
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