American Society of Landscape Architects: Welcome Annotated

A green roof replaces traditional roofing with a lightweight, living system of soil, compost, and plants.

The plants–and the dirt and gravel that hold them–filter rainwater and some of its pollutants. The plants produce oxygen that help clean the air. A green roof reduces a building’s heating and cooling costs, acting as a form of insulation. And they lessen the heat island effect, in which buildings warm up so much that they heat the surroundings.

Explore the Benefits of a Green Roof