Green Roofs Selection Guide

Green roofs are environmentally friendly roofing alternatives that comprise of different functioning layers with the topmost layer being some variety of greenery. The functions of green roofs are immense; however, they all provide beneficial functionality to the building they are a part of, the residents of the building, and their surrounding environment. There are six basic layers to a green roof: the waterproofing membrane, the root barrier, the drainage and water retention layer, the filter fabric layer, the growing medium, and the vegetation. There are numerous economic, social, and environmental advantages to having a green roof. However, some consider the high initial cost as a negative. There are three main types of green roofs: extensive, semi-intensive, and intensive. Extensive green roofs are lightweight, low-maintenance, low cost, and often include a thin layer of soil and drought-tolerant plants. Semi-intensive green roofs have a slightly higher weight, require more maintenance, and a higher cost than extensive green roofs. They also sustain small herbaceous plants and shrubs. Lastly, intensive green roofs are the most elaborate type and can support a wider variety of plants including trees and flowers. They require deeper soil and more maintenance, but they offer additional recreational spaces that are accessible to people. This paper can be used as a guide for people who are interested in building a green roof on their new or existing building. It can serve as a starting point for figuring out which type of green roof is best for them.