Green Roofs & Walls

A green roof can be defined as a system where a vegetation is incorporated into a roof, usually comprising the vegetation itself supported by a growing medium, filter sheet, drainage/reservoir layer, root barrier and

waterproof membrane.

There is a spectrum of different types of green roof, broadly ranging from intensive to extensive – a reference to the degree of maintenance they require. Intensive roofs (roof gardens) consist of lush vegetation on a comparatively deep and relatively nutrient rich substrate which can accommodate shrubs and even trees. They can require significant increases in load bearing capacity and ongoing management, including irrigation and application of fertiliser. Extensive roofs often have a shallow to medium depth substrate and are designed to be relatively selfsustaining. They require minimal maintenance and often only initial irrigation for establishment purposes. In addition, there are numerous permutations for intermediate treatments typically referred to as semiintensive or simple-intensive green roofs.

Interest is growing in the potential for green roofs and walls to improve the urban environment through their multiple benefits. These include:

• enhanced building energy efficiency resulting from their insulation properties, and evapo-transpiration which reduces cooling loads;
• the potential to ameliorate surface water run-off and improve water quality, thereby comprising an important component of sustainable drainage systems (SuDs);
• amelioration of the urban heat island effect due to micro-climatic cooling;
• improvement in air quality

For more detailed information on these topics please see the related documents and pesentations pane(s) on the left.