NEW YORK – When owners of the Empire State Building decided to blanket its towering facade this year with thousands of insulating windows, they were only partly interested in saving energy.

They also needed tenants.

After 78 years, Manhattan's signature office building had lost its sheen as one of the city's most desirable places to work. To get it back, the owners did what an increasing number of property owners have done — they went green, shelling out $120 million on a variety of environmental improvements, a move would have been considered a huge gamble a few years ago.