About 93 percent of 3, 040 large U.S. hospitals used one or more day lighting or lighting conservation features, including tinted window glass (80 percent), reflective window glass (39 percent), external overhangs or awnings (47 percent), skylights or atriums designed to provide light (57 percent), automatic controls or sensors that increase or reduce lighting in response to the level of natural light (14 percent), and occupancy sensors that reduce lighting when rooms are unoccupied (46 percent).