In 2012, when NPR moves to its recently acquired headquarters site seven blocks east of its present home, it will have much more room for growth than it had after its last move, with as much as four times the floor space. In 1994, when the network moved into its present home, 635 Massachusetts Ave. N.W., it had about 400 employees. The building, with less than 150,000 square feet, could accommodate just 480, NPR said at the time. The space was soon outgrown.