Green roofs, or roof gardens, are a layer of vegetation that sits atop a building's roof. They usually include a waterproofing layer, a root barrier, a growing medium and a drainage system that acts as an extension of the existing roof. They can also include an irrigation system, depending on the types of plants used. In addition to providing aesthetic appeal, green roofs can also add a lot of functionality to a roof.
- provide thermal insulation to a home or office building
- retain storm-water that would otherwise add to the city's waste-water management system
- attract wildlife
- decrease the amount of heat radiated back into a neighborhood (think cool field of grass versus hot asphalt)