The University of Iowa's Visual Arts Building, by Steven Holl Architects and BNIM has received LEED Gold certification by the United States Green Building Council. It is the western hemisphere’s first voided active slab heating and cooling system. “The efficient system places plastic bubble-­shaped forms, arranged in a grid, at the center of the slab’s depth—where concrete is least effective—to span farther with the same thickness. “In this building, we were able to use 25 percent less concrete,” says Kelley Gipple of Structural Engineering Associates. Reduction in concrete could, however, be as high as a third.”

Here are more interesting metrics about The project.