Outdoor space for Manhattan office buildings is rare, but the Empire State Building now has four green roofs: two 3,450 sq. ft. green roof terraces on the 21st floor (pictured) with patios and outdoor furniture; a 1,000 sq. ft. green roof on the northwest side of the 25th floor; and a 1,200 sq. ft. green roof on the west side of the 30th floor.

The lofty spire on the 1931 Art Deco building is a vertiginous 1,454 feet above the intersection of Fifth Avenue and West 34 Street. King Kong likes to climb it; and Cary Grant and Tom Hanks set rendezvous with women there to tug at the heartstrings of several generations of moviegoers. Yes, it's the iconic and a little long in the tooth Empire State Building, probably the world's most famous office building.

To continue to attract corporate office tenants, the building owners, Empire State Building Associates L.L.C (traded on the NYSE as Empire State Realty Trust Inc. – ESRT), have invested in extensive energy and infrastructure upgrades, spruced up public areas and added amenities totaling more than $550 million.

The building owners partnered with the Clinton Climate Initiative, Rocky Mountain Institute, Johnson Controls and Jones Lang LaSalle to develop a comprehensive energy efficiency retrofit to reduce the building's total energy consumption by 38 percent. The building has received an Energy Star rating of 80, placing it in the top 20 percent tier of energy efficient buildings, as measured by the Energy Star program. The energy retrofit was an important factor in the building receiving LEED-EB Gold certification.

Of particular interest to landscape architects, however, are the four green roof terraces new to the historic building.

Rainer Gerbatsch, RRC, LEED AP, president, Commercial Roofing Solutions, Inc., Clifton, N.J., roofing and waterproofing consultant for the project, said the green roof system is well engineered and has the strength and durability for the challenging conditions. The engineering for these lightweight, prevegetated mats (Xero Flor Green Roof System) was originally designed in Germany and refined over more than 40 years in tens of thousands of rooftop installations around the world. All system components for projects in the U.S., however, are 100 percent American-made.