The Empire State Building, for four decades the world’s tallest and still the tallest in New York, is spending $13 million on windows, insulation and other upgrades to cut energy use by 38% and save about $4.4 million a year. Never has a structure so old and so tall gone so green. “It’s the most recognizable building energy retrofit in the world,” says Arah Schuur, director of a conservation program at former president Bill Clinton’s foundation. – from USAToday