April 7, 2009 - A $20 million energy efficiency overhaul at the Empire State Building is expected to save $4.4 million and more than 100,000 metric tons of carbon dioxide over the next 15 years.

The upgrades planned for the Empire State Building include replacing all of the skyscraper's 6,500 windows with a type of insulated glass that reduces summer heat load and winter heat loss. Extra insulation will be installed behind radiators to save heat, and other changes are planned for the building's ventilation, chilled water and lighting systems.

Work already has begun, with the upgrades to the building systems expected to be completed by the end of 2010.

The Empire State Building isn't the only iconic American skyscraper due for a green makeover. The owners of Chicago's Sears Tower are considering a range of cost-cutting green upgrades, including an energy-saving paint job.