Going with Green Roofing

I'm glad to hear that a new bank headquarters opening up in Annapolis will be the first commercial building to include a green roof (via Blog Arundel). Indeed, I've wondered why more buildings in America don't have them, given all the clear benefits -- e.g., catching run-off, reducing heat, aesthetics, etc. Apparently, however, buildings with green roofs have specific structural requirements in order to accomodate all the extra weight, which makes it difficult for some kinds of buildings, especially older ones, to be retrofitted with them. The problem is not unlike that of hybrid cars: The technology is there, it's turning over the current fleet of (non-fuel efficient) cars that will take time -- time we may not have.