A basic green roof, or extensive green roof, has less than six inches of soil substrate and is designed to be low maintenance. Its primary objective is to provide energy savings and can easily integrate with solar panels. An intensive green roofing system has more than six inches of soil and includes more bio-diversity in its vegetation. This system goes beyond utilitarian goals striving to ad aesthetic value as well. These systems become gardens that can support trees creating open spaces to use and new habitats for a variety of species. However, with a green roofing system you must always keep in mind the extreme environment that the vegetation will be in and chose the vegetation accordingly. All selections should be drought-tolerant, hardy plants selected with the aid of a knowledgeable, licensed landscape professional.