The U.S. Green Building Council, as it kicks off its annual Greenbuild conference this week, is announcing a major milestone: its certified commercial buildings now exceed 1 billion square feet. Another 6 billion or so square feet of projects are registered around the world under the private group's LEED (Leadership in Energy and Environmental Design) program, one of the most comprehensive and best-known green building standards. "This traction demonstrates the transformation of the way we design, build and operate buildings," said Rick Fedrizzi, the group's president and CEO, in a statement. "Not only does green building contribute to saving energy, water and money, it also creates green jobs that will grow and energize our economy." LEED's rapid growth continued, albeit at a slower pace, during the recent U.S. economic downtown, according to the group's data. Since it was introduced in 2000, more than 36,000 commercial projects and 38,000 single-family homes have participated and of those, 7,194 commercial projects and 8,611 homes are complete and have met the criteria. LEED requires reductions in energy and water use as well as recyclable, locally sourced and non-toxic building materials.