Study Reveals Valuable Lessons for Designing Energy Efficient Buildings

U.S. Dept. Energy
July 7, 2006

Findings from a recently-released study of low-energy, high-performance commercial buildings in the United States reveal that, while the buildings do save energy as designed—25 to 70 percent lower energy consumption than allowed by code—more can be done to achieve the Department of Energy's (DOE) goal to achieve marketable zero energy buildings by 2025.

The study, commissioned by DOE's Building Technologies Program and conducted by the National Renewable Energy Laboratory (NREL), analyzed six buildings that represent the current generation of low-energy commercial structures. These buildings were designed to meet low-energy and sustainability goals by using innovative combinations of energy technologies such as daylighting, radiant heating, natural ventilation, photovoltaic systems, evaporative cooling, and passive solar strategies.

"Commercial buildings account for 18 percent of total energy consumption in the United States, with lighting and heating being primary energy-consuming activities," said David Rodgers, manager for the DOE's Building Technologies Program. "With this study we've learned how well a sampling of today's model low-energy buildings actually did on meeting their original energy goals. Using this 'baseline,' we can now supply a set of best practices to commercial builders to make future low-energy buildings even more efficient."

The six buildings in the NREL study were the Adam Joseph Lewis Center for Environmental Studies, Oberlin College, Ohio; the Visitor Center at Zion National Park, Springdale, Utah; the Cambria Department of Environmental Protection Office Building, Ebensburg, Pennsylvania; the Philip Merrill Environmental Center, Chesapeake Bay Foundation, Annapolis, Maryland; the Thermal Test Facility, National Renewable Energy Laboratory, Golden, Colorado; and the BigHorn Home Improvement Center, Silverthorne, Colorado.

Key lessons outlined in the report, Lessons Learned from Case Studies of Six High-Performance Buildings, include:

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Owners provide the main motivation for designing and constructing low-energy buildings;
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Setting measurable energy saving goals at the outset of the project is crucial to realizing low-energy buildings;
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Many decisions about including or not including building features are not motivated by cost;
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Today's energy-saving technologies can substantially change how buildings perform when they are applied together and properly integrated in the design, installation, and operation of the building;
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An integrated whole-building systems design approach is needed to achieve energy goals;
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Buildings do not always operate as they were designed (e.g., plug loads are often higher than planned, daylighting energy savings might be lower, occupants do not follow energy savings strategies as instructed); and
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Energy performance must be tracked and verified following completion of construction.


"In the United States, new commercial buildings are added to the building stock faster than old buildings are retired," added Rodgers. "Conducting research to evaluate the state-of-the-art in energy-efficient buildings as we know it now puts us in a better position to inform the next generation of low-energy commercial buildings."

This study—along with a network of partners in state government, research, academia, construction, design, and utilities—support DOE's goal to create the technology and knowledge base for marketable zero-energy commercial buildings by 2025. Zero energy buildings are designed, constructed, and operated to generate the same amount of energy they use each year, resulting in a net-zero energy consumption.

The full NREL study report, including case studies for each building, detailed lessons learned, and additional information on zero energy buildings and daylighting technology, can be viewed here.