I live in a seven unit, flat-topped, rubber-roofed, brick condo building in Boston, and my girlfriend (who also lives here) has mentioned the possibility of a rooftop garden, or maybe just rooftop sod, as an energy saving measure. All the heating costs are included in the condo fee, so everyone in the building has an interest in conserving energy. We've just moved into the building, so we don't know the other residents' thoughts on the matter, but I think it is safe to think that energy conservation is a priority for all. I don't really know anything about rooftop gardens/sod. Does anyone have any advice/info? Or maybe some other websites with information?