The Nature Conservancy's energy-efficient Indiana headquarters has been certified with a top energy rating for innovations that include three wind turbines.

Nature Conservancy Indiana director Mary McConnell said the downtown Indianapolis building has received a platinum-level certification under U.S. Green Building Council guidelines known as Leadership in Energy and Environmental Design, or LEED.

She said the Efroymson Conservation Center's certification for its energy and water-efficient features makes it Indiana's most energy-efficient building. The $5.7 million center opened in 2010 with efficiencies that include a geothermal system that taps the Earth's natural heat storage capacity to both heat and cool the 20,000-square-foot building.

The group added the wind turbines to a stormwater-collecting garden outside the headquarters at 620 E. Ohio St. in 2011.

Since its founding in 1959, the conservancy's Indiana chapter has protected through acquisition about 70,000 acres of Indiana forests, wetlands, caves and prairie harboring rare or endangered plants and animals.