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Updates include replacing all 6,500 windows to reduce summer heat load and winter heat loss. Tenants in the building will also be able control their own power on a new web-based system, so that energy can be managed more efficiently.

Mayor Michael Bloomberg said he hopes the $20 million project will serve as a model for buildings around the world.

The goal is to cut energy use by 38 percent, which will save $4.4 million a year in energy costs.

Former President Bill Clinton, who was also on hand for the announcement, said that the move is not only smart environmentally, but also economically.

"Right here before us is, ironically in this economic time, the biggest job generator is in building retrofits," said Clinton. "It will create millions and millions of jobs. It will put millions of Chinese factory workers who have lost their jobs because American demand has collapsed back to work."

The building will use private money to fund the initiative.