Building an affordable, comfortable home that produces as much energy as it uses is no longer the home of the future, but the home we need now.

One of the timeliest initiatives emerging recently from Oak Ridge National Laboratory (ORNL), in Oak Ridge, Tennessee, began with a collaboration with Habitat for Humanity to develop energy-efficient technologies for five homes in Lenoir City, Tennessee. To date, results of this effort, championed by ORNL researcher Jeff Christian, have shown great promise and have now expanded to include seven more commercially built homes in Oak Ridge and Knoxville, Tennessee.

It all started in 2002, when all of ORNL’s building research projects were consolidated and challenged to develop “the zero-energy house”—one that would use only the energy it produced. Believing that energy-efficient homes should be affordable for working families, Christian quickly seized this challenge and argued that unless the issue of residential energy consumption is addressed now, it will likely grow by 1 percent per year until 2025. Even more alarming, the annual rate of consumption for commercial energy is forecast to be twice that figure in the same period.

“Yes, we must replace oil with biofuels. Yes, we must pursue other supply-side solutions in an environmentally acceptable manner,” Christian said. “But there’s enormous potential to reduce energy demand in our homes and offices. That’s by far the cheapest solution to address this problem.”

Consequently, five low-energy homes were built in a Tennessee community between 2002 and 2005, the result of the Habitat for Humanity partnership and funds from the Tennessee Valley Authority. The community became a “living laboratory” for ORNL researchers studying the impact of energy-efficient building practices and technologies. Their work has so far produced impressive real-world results. In some homes, electric bills declined to less than 50 cents a day. “Creating more energy-efficient buildings is not only part of the overall solution, it’s the most cost-effective opportunity to reduce the nation’s energy consumption and affect climate change,” Christian stated.

The latest project involves three research houses built in 2008 at Campbell Creek in Knoxville. The first is a typical Energy Star “builder house” with an energy efficiency score of 85 Home Energy Rating System (HERS). The second “retrofit house” with energy-efficient upgrades has a HERS rating of 64 (the lower the better). The third, a “high performance” house with technologies pushes the HERS rating to 30, or about 55 percent savings compared to the “builder house.” Both the second and third houses, because they have HERS ratings of less than 70, were awarded EnergySmart Home Certificates for their reduced energy use under the DOE Building America Builders Challenge Program.

“With these three houses in a typical residential setting we will have research capabilities that are world-unique,” Christian said. “And the really exciting thing is that these houses will be available for research for seven years, so we will be able to replace, test and accelerate the development of even more efficient component technologies.” In the United States buildings command 40 percent of the country’s overall energy use, outstripping industry at 32 percent and transportation at 28 percent. Buildings also produce 43 percent of U.S. carbon emissions, using 38.8 quadrillion British thermal units (BTUs) of energy each year for heating, cooling, ventilation, lighting, water heating, refrigeration and other energy demands. Obviously, a residential housing community is the logical place to launch a zero-energy project.

ORNL works with industry partners to develop the construction materials and technologies needed to build greener homes. Researchers have tested solar-reflective roofing, insulation materials, structural insulated panels, solar technologies and foundation systems. The laboratory has developed software tools to assess moisture-resistant construction materials, provide energy efficiency ratings for buildings, design more efficient heat pumps and other equipment and guide development of standards for building insulation, materials and moisture design.

Meanwhile, Christian and his team are carrying out their work in support of an ambitious U.S. Department of Energy program to develop affordable, net-zero-energy housing by 2020 and zero-energy commercial buildings by 2025. The Habitat homes feature renewable energy sources to minimize demand for fossil fuels, such as heat pump systems that tap geothermal energy in the ground and solar panels to provide electricity and water heating capabilities. Energy-efficient construction and technologies are incorporated, including roofs with “cool-color” coatings to deflect heat, utility walls that consolidate most of the homes’ major plumbing (alone providing an energy saving of 15 percent) and virtually airtight construction with advanced ventilation systems to keep the homes comfortable.

“I’ve noticed that when I tell people that these new houses have energy costs of approximately 50 cents a day, they tend to think about their own homes,” Christian commented. “People respond to the idea. They just need education and awareness.”