Former President Bill Clinton and Mayor Michael Bloomberg are hoping that the environmental changes at the iconic skyscraper will serve as a model for buildings around the world.
The updates include replacing 6,500 windows to reduce summer heat load and winter heat loss.
Tenants in the building will also be given individualized Web-based power usage systems so that energy can be more efficiently managed.
The goal is to cut energy use by 38 percent. The $20 million project is expected to save $4.4 million annually in energy costs.