WHAT ARE THE BENEFITS OF GREEN ROOFS?
Green roofs provide a number of benefits to the built environment including wildlife, air quality, stormwater, and mental respite. The benefits they offer can be categorized in the ‘Triple Bottom Line’ theory of sustainability: People, Planet, Profit. Picture that green roofs are replacing the green space taken up by the building footprint, on the roof.
WILDLIFE BENEFITS
Green roofs and gardens create habitat for wildlife. Pollinators, birds, insects, and small animals are all attracted to vegetated areas for shelter. If herbaceous plant material such as wildflowers are present, pollen is provided for pollinators, plant material is provided for insects, and seeds are provided for birds and small animals. In cities vegetated areas can be disconnected by roads, buildings, and parking lots. Wildlife need to travel in search for food, water, and shelter. These disconnected areas can be dangerous for wildlife while traveling and can be fatal. Green roofs connect these areas by protecting and encouraging the travel of wildlife.
BENEFITS TO AIR QUALITY
Green roofs and roof gardens are covered in plants. Through photosynthesis, plants absorb carbon dioxide in the air and release oxygen. Traditional roofs and other hard, reflective surfaces reflect sun rays. These sun rays produce heat, creating higher heat levels in the urban environment also know as "Heat Island Effect." Plants can reduce the impact of the "Heat Island Effect." Plants go through a process called "evapotranspiration." Through evapotranspiration, plants use heat energy to evaporate water thus decreasing the impact of the heat in the atmosphere. Dust and air pollutants exist in the air and can impact air quality negatively. Plants filter out and absorb airborne dust and air pollutants.
BENEFITS TO URBAN WATER SYSTEMS
Green roofs and roof gardens have a thick layer of soil (<4" is intensive, >4" is extensive) and a mat of plant material. This system retains water from rainfall. The rainwater is slowed down in velocity and reduced in quantity, therefore having a positive impact on urban stormwater systems and downstream erosion. By filtering the rainfall through the green roof the amount of pollutants entering the water way decreases.