Half-way through the EPA's yearlong challenge to spur energy efficiency in existing buildings, the University of Central Florida and Scientific Instruments have both hit the 30 percent mark for energy savings to date.

At the mid-point, the 245 buildings enrolled in the EPA's "Battle of the Buildings" challenge have saved a cumulative $3.7 million in energy costs, and cut greenhouse gas emissions by an amount equivalent to those generated by 2,300 homes in a year.

"Competitors in the second year of the Energy Star Battle of the Buildings are already achieving energy-savings that really pack a punch," EPA Assistant Administrator for Air and Radiation, Gina McCarthy, said in a statement. "The stories behind these energy-savings speak to the dedication of American businesses and organizations to protecting the environment and public health, and to economic common sense."

The two organizations at or above the 30 percent mark are leading the challenge, and the EPA this week released the results for the top 12 contenders. The list shows the breadth of the range of contenders, from parking garages to churches to retail stores -- and shows how much farther the leaders have come.

The chart below lays out the current top contenders, with the percentage of energy reduction tallied to date:

• University of Central Florida Garage C (Other): Orlando, Fla. 31%
• Scientific Instruments (Office): West Palm Beach, Fla. 30%
• Jackson Creek Middle School (K-12 school): Bloomington, Ind. 26%
• USE Credit Union (Bank): San Diego, Calif. 20%
• North Suburban Medical Office Building (Medical Office): Thornton, Colo. 18%
• Office Depot (Retail Store): Plano, Texas 17%
• Hammond U.S. Courthouse (Courthouse): Hammond, Ind. 14%
• First Unitarian Society of Minneapolis (House of Worship): Minneapolis, Minn. 14%
• St Mark's Medical Center (Hospital): La Grange, Texas 10%
• Norandex (Warehouse): Rochester, N.Y. 8%
• Kenan Residence Hall at UNC (Dorm): Chapel Hill, N.C. 3%
• The Colonnade Hotel (Hotel): Boston, Mass. 2%

Last year's winner, the Morrison Hall dormitory at the University of North Carolina-Chapel Hill, achieved an overall 35.7 percent energy reduction over the course of the year-long challenge. Among the methods the school used to make such a drop included a lighting retrofit that replaced 64-watt CFLs with 13-watt CFL, and Improving the efficiency of HVAC systems, including variable air volume systems and air economizers.

The National Building Challenge runs through November; all the participants are chronicling their efforts and strategies through social media like Twitter and Facebook. To follow the contenders in the Battle of the Buildings contest, visit http://www.energystar.gov/BattleOfTheBuildings .