Green roofs can be classified by their purpose and characteristics in to two major types: intensive roofs and extensive roofs [8,51]. Intensive roofs need a reasonable depth of soil and require skilled labor, irrigation, and constant maintenance. They are usually associated with roof gardens [20]. Extensive roofs have a relatively thin layer of soil, grow sedums and moss and are designed to be virtually self-sustaining and require minimum maintenance [20]. There is a third type of green roofs called semi-intensive. Semi-intensive green roof is a combination of extensive and intensive, however the extensive type must represent 25% or less of the total green roof’s area [51].