... Rockefeller Center in NYC is installing a 1 500sqm green roof; in San Francisco a developer’s winning proposal for a mixed-use complex of office towers was aided by inclusion of a park about the size of 4 rugby fields 7 stories above the main bus platform. In a 2005-2006 study, U.S. green roofs grew by 25 percent from the year before. Tokyo now requires 20 percent of roof surfaces to be green. In Germany, 7 percent of roof space is already green.

Green roof benefits: Reduced energy costs by keeping the roof cooler in summer, reduced heat island effect, longer roof life, (University of California researchers reported that green roofs can double the life of a roof from 15 years to 30 years), stormwater capture and pollution filtration, improved air quality.
Green drawbacks:  higher upfront costs and figuring out how to get either the grass-eating goats or your landscape maintenance crew up on the roof ...