Green roofs have many benefits. Their major benefit is to reduce the rapid runoff of rainwater from roofs by storing the water in the soil or gravel, and releasing it slowly. This helps to prevent flooding in urban areas, which is becoming a greater concern due to global warming. As well as reducing rainfall runoff, they help to improve air quality by bringing plants into the city areas and they also have a major biodiversity benefit by providing habitats for wildlife such as insects and birds. Green roofs also improve energy efficiency by providing insulation to the building beneath them. All these benefits are shared by green walls, but there is generally less of an effect with them, due to the limitations of a vertical surface.
Green roofs come in various forms. They can be simply a low maintenance thin layer of gravel which will support low growing plants such as sedum, and which only need an annual weeding to keep them working; or they can be a more ambitious affair with shrubs and even small trees, which can act as a rooftop garden or green haven in the 'urban jungle'. Provided the proper support has been built into the roof by a qualified engineer, there is no danger of roofs collapsing under the weight of soil or other material.
Green roofs originated in Iceland, where the inhabitants simply covered their roofs in green turf to provide insulation in the harsh environment. Since those humble beginnings, green roofs are rapidly being adopted in their various modern forms around the world as an essential part of the move to a more sustainable lifestyle.
(Images from Sadhbh)
|Green Roof from Iceland where the concept began|
|Cross Section of green roof|
|Cross Section of Green roof|