Students learn about green roofs by learning beneath them in Malmö, Sweden. Notice the solar thermal panels on the roof as well. Since the efficiency of solar PV panels drops as they heat up, there is some evidence to indicate that solar and green roofs make a great combination - the green roof cools the roof surface, increasing the electrical output of the PV panels, while the shading of the panels provides a mixed sunny/shadow environment, incerasing the biological diversity within the green roof. (photo by Jim Mueller, Vulcan)