ADELPHI LABORATORY CENTER, Md. -- Construction in December atop Building 601 at the Army's Adelphi Laboratory Center in Maryland features a solar thermal roof, a renewable energy project that will save money and conserve natural resources.

The roofing system is expected to annually save more than 170 million British Thermal Units, which is equivalent to approximately 30 barrels of crude oil - a cost savings of $3,500 at current oil prices.

Unlike a typical photovoltaic system, which converts sunlight to electricity, a solar thermal roof uses solar energy to heat air, said Steve Rebetsky, ALC Directorate of Public Works mechanical engineer, who is managing the construction project. The construction of the roof relies on standard methods with a few modifications.

A dark-colored standing-seam metal roof is constructed over the existing roof, but a flexible radiant barrier is installed under the support structure, creating a gap where the air is heated by the sun to approximately 40 degrees Fahrenheit above the ambient air temperatures.

A control system and circulating fans then pump the air to the various mechanical systems and interior spaces of the building. The heated air is then used within the building to reduce the required heating load.

During the winter, the system will pre-heat fresh outside air that is used to maintain proper building ventilation. The solar heated air will be used to heat water for domestic use and for the heating, ventilation, and air conditioning systems.

It will also directly heat the main mechanical room and boiler combustion air, resulting in increased boiler efficiency. During the summer, when the sun is most intense, the radiant barrier will prevent more than 90 percent of the heat from entering the building and at the same time, since heating requirements are at their lowest, exhaust any excess heated air to the atmosphere.

The 601 roof is one of the first such solar thermal roof projects to be constructed for an office building in the United States, according to the project manager with American Solar Inc., the company installing the system.

"With the successful completion of this project we hope to further the Garrison's use of renewable resources and, in addition to solar thermal roofs, expand to other renewable energy projects utilizing photovoltaic, solar water heating and solar lighting," said Ken Noppenberger, ALC director of public works. "This will help us continue to not only meet DoD energy goals, but also conserve electricity, natural gas, oil, etc."