Architects aim to reclaim the original energy-saving features of the 1917 U.S. General Services Administration buiding, including natural lighting and ventilation.With $25 billion in annual power and fuel costs, the U.S. government is the largest single energy consumer in the nation's economy, and among the largest in the world.The Obama administration now is seeking to ramp up that effort dramatically—with the help of an unprecedented $4.5 billion in stimulus funds to be spent by next September entirely for federal green building and renovation projects. By executive order, the federal government is aiming to reduce its greenhouse gas emissions by 28 percent by 2020. National Geographic.