Toronto's Green Roof Bylaw
Toronto is the first city in North America to require that all new buildings incorporate a green roof. This bylaw came into effect in 2009 and there are currently 135 completed green roofs in the city. Benefits of green roofs include reduced storm water runoff, reduced energy consumption, better air quality and increased green space.
Green roofs can be either Intensive or Extensive. Intensive roofs can be used for recreational purposes and support vegetation with deep roots, such as trees. Extensive roofs are designed for plants with shallow roots. They require less maintenance and are lighter and less expensive to install.
While new buildings often use a complete green roof system (all parts of the roof support plant growth), retrofitting an older buiding can involve a modular system (trays of plants grown off-site are placed on the existing roof) or vegetation blankets (rolls of plants are set on the existing roof). For more information see the City of Toronto's What is a Green Roof?
The Business, Science and Technology Department has a great selection of books about designing and constructing green roofs and living walls. Green Roofs: Ecological Design and Construction features Toronto as a Municipal Case Study, and the three green roofs discussed are Mountain Equipment Co-op, Queen's Quay and City Hall.