Green roofs have a layer of plant material that absorbs water like a sponge. They capture water when it rains, slowly releasing it through evaporation and plant use. Green roofs can significantly reduce the amount of rain water that would otherwise run off an impervious roof surface. Green roofs can also help reduce building energy usage and noise levels, while increasing the durability and lifespan of the roof compared to conventional roofs.Green roofs are being increasingly used in urban areas where space constraints limit the use of other stormwater management practices.
The greater insulation offered by green roofs can reduce the amount of energy needed to moderate the temperature of a building, as roofs are the sight of the greatest heat loss in the winter and the hottest temperatures in the summer.
The presence of a green roof decreases the exposure of waterproofing membranes to large temperature fluctuations, that can cause micro-tearing, and ultraviolet radiation.
Green roofs have a much lower burning heat load (the heat generated when a substance burns) than do conventional roofs (Köehler 2004).
Green roofs have excellent noise attenuation, especially for low frequency sounds. An extensive green roof can reduce sound from outside by 40 decibels, while an intensive one can reduce sound by 46-50 decibels (Peck et al. 1999).
Green roofs can sustain a variety of plants and invertebrates and provide a habitat for various bird species. By acting as a stepping stone habitat for migrating species they can link species together that would otherwise be fragmented.
Green roofs can increase a building’s marketability. They are an easily identifiable symbol of the green building movement and can act as an incentive to those interested in the multiple benefits offered by green roofs.
Green roofs on educational facilities can provide an easily accessible sight to teach students and visitors about biology, green roof technology, and the benefits of green roofs.