Construction on the Empire State Building began March 17, 1930 and was finished in just under 15 months. A recently completed, comprehensive retrofit program, which included installation of green roofs, is designed to make the building 38 percent more energy efficient.

Towering 1,454 feet above Manhattan, N.Y., the Empire State Building is one of the most recognizable buildings in the world. And now with new investments in energy efficiency and building-wide infrastructure upgrades, it is one of the greenest.

The Empire State Building partnered with the Clinton Climate Initiative, Rocky Mountain Institute, Johnson Controls and Jones Lang LaSalle to develop a comprehensive energy-efficiency retrofit program that will reduce the building's total energy consumption by 38 percent.

The $550 million retrofit includes 6,500 windows rebuilt on site for greater energy efficiency, improvements to the building-wide mechanical and electrical systems, and the installations of green roofs, which decrease stormwater run-off and improve water quality in New York's waterways, moderate the urban heat island effect, filter dust and other air pollutants, and store carbon dioxide and other forms of carbon to reduce greenhouse gases.

These efforts have led to an Energy Star rating of 80, placing it in the top 20 percent in energy efficiency among all buildings measured under the program. The energy retrofit was also an important reason the building received the LEED-EB Gold certification from the United States Green Building Council. All information and monitoring and verification reports can be viewed at www.esbsustainability.com.