The hills are alive with lush greenery — and so are the rooftops. Green or living rooftops, long popular in Europe, are becoming common with both private and business owners. The green roof industry grew by as much as 28 percent in 2010. Why? Green rooftops , which are relatively thin layers of greenery affixed onto a roof, can act as effective insulators, thus reducing energy costs. They also last longer and can absorb stormwater, acting as valuable drainage systems. Green rooftops also can provide a pleasant escape for inhabitants of an urban jungle.