"About a third of New York's building supply was built before 1939-long before sustainability and greenhouse gases were on anyone's radar screen-and very little of it can be classified as green. That's true of the newer housing stock too, for that matter; a recent study showed that New York trails many other major cities in its number of LEED buildings and green housing options.
Which means that nearly 80 percent of New York City's carbon footprint comes from its energy-guzzling buildings. Thus the mayor announced last month that buildings bigger than 50,000 square feet would undergo a major overhaul, joining cities like Los Angeles and Seattle in a massive green building retrofit. Following the lead of the federal government (and inspired in part by stimulus funds), New York will now attempt to make existing buildings energy-efficient, lower their greenhouse gas emissions and remove their toxic innards."