Green Roof Overview
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Toronto’s leadership in green roof policy began with the development of a Green Roof Strategy for the city which would lay the foundation for requiring green roofs on new development in 2009.
The Green Roof Strategy (2006)
In February, 2006, Toronto City Council adopted Toronto’s Green Roof Strategy to encourage the construction of green roofs on City and privately owned buildings through incentives, public education and the development approval process. The Green Roof Strategy called “Making Green Roofs Happen” was developed after a study, commissioned by the City and undertaken by a team from Ryerson University, indicated that widespread implementation of green roofs in Toronto would provide significant economic benefits to the City, particularly in the areas of stormwater management and reducing the urban heat island and associated energy use for cooling.
The results of this study prompted the City to hold two stakeholder workshops to help to define criteria for green roofs, and identify barriers and solutions to green roof implementation. Through a process of extensive stakeholder consultation the City produced the Green Roof Strategy proposing options for implementing green roofs. The initiatives in this strategy fall into four main categories:
- A pilot incentive program;
- Installation of green roofs on City/ABC buildings;
- Use of the development approval process to encourage green roofs; and
- Publicity and education
Green Roof Pilot Incentive Program
A key outcome of the Council’s Green Roof Strategy was that a Green Roof Incentive Pilot Program be created to encourage the installation of green roofs by the private sector. The pilot program, funded by Toronto Water, was initiated in 2006 and offered a financial incentive of $10/m² . The 2006 program was very successful and awarded grants to 16 applicants, resulting in the construction of 3,000 m² of green roofs. The program would later become the EcoRoof Incentive Program.
Installation of green roofs on City/ABC buildings
The City’s green roof policy requires new buildings constructed by the City and its Agencies, Boards and Commissions to provide a green roof covering 50% of all Available Roof Space. The first of many green roofs installed as a result of the Green Roof Strategy were:
- York Civic Centre, 2700 Eglinton Ave, (204 m²);
- Gladstone Library, 1101 Bloor St, (176 m²); and
- Toronto Botanical Gardens, 777 Lawrence Ave., (223 m²)
Use of Development Review process to encourage green roofs
When Council approved the Green Roof Strategy, it also directed that green roofs be achieved on new development through the approval of zoning by-law amendments and site plan control applications. In 2007, 14 green roofs were approved through the planning process.
Promotion and Awareness
The Green Roofs Strategy identified a number of initiatives to promote green roofs in the city, including creating a green roof web page, technical workshops and staff training. The City established a website and held 2 in-depth ‘Green Roof 101’ training sessions for a cross section of city staff. The training session provided information on green roof benefits and their design and construction.
In 2007, in recognition of its exemplary efforts in developing and promoting the Green Roofs Strategy, the City of Toronto was awarded the Federation of Canadian Municipalities FCM CH2Hill Sustainable Community Award. This award recognizes leadership in sustainable community development and gives national recognition to projects that demonstrate environmental excellence and innovation in service delivery.
In 2013, the City developed the Guidelines for Biodiverse Green Roofs to expand the awareness of design strategies to enhance habitat opportunities within green roof design.
City of Toronto Green Roof Bylaw (2010)
In 2006, amendments made by the Province of Ontario to Section 108 of the City of Toronto Act (COTA), provided Council with the authority to pass a by-law requiring and governing the construction of green roofs. The new authority under COTA allowed the City to require green roofs as-of-right as opposed to the previous approach of encouraging green roofs for new private development. The provincial authority was specific in allowing the City to set standards only for green roofs. This is an “exception” to the Building Code Act, 1992 which generally prohibits municipal bylaws exceed the requirements of the Ontario Building Code.
The Green Roof Bylaw supports the implementation of city-wide environmental policy objectives of the Climate Change, Clean Air and Sustainable Energy Action Plan, Transform TO and the Wet Weather Flow Management Master Plan. The City’s Official Plan also supports the use of green roofs as an innovative approach to reducing the urban heat island effect in Toronto.
In 2009, following extensive consultation with stakeholders City Council unanimously adopted the Green Roof Bylaw. Toronto became the first city in North America with a bylaw that both requires green roofs and establishes the construction standards for them.
As of 2016, the City of Toronto has received approximately 400 applications for green roofs constructed under the Green Roof Bylaw.
For more information on the City of Toronto Green Roof bylaw
What is a Green Roof?
A green roof is a roof of a building that is partially or completely covered with vegetation and a growing medium, planted over a waterproofing membrane. Toronto’s Green Roof Bylaw defines a green roof is an extension of an above grade roof, built on top of a human-made structure, that allows vegetation to grow in a growing medium and which is designed, constructed and maintained in accordance with the Toronto Green Roof Construction Standard. A green roof assembly includes, as a minimum, a root repellent system, a drainage system, a filtering layer, a growing medium and plants, and shall be installed on a waterproof membrane of an applicable roof.
Types of Green Roofs
Green roof systems are generally classified as extensive, semi-intensive or intensive.
Extensive Green Roofs
Extensive green roofs have a shallow growing medium and generally use plant communities designed to tolerate the intense sun, wind and drought conditions of a roof environment. Extensive green roofs are lighter, require less structural support and need less frequent maintenance. The costs are lower than intensive semi-intensive green roofs. Plants generally consist of mosses and succulents.
Semi-Intensive Green Roof
Semi-Intensive Green Roof fall in between Extensive and Intensive Green Roof systems. More maintenance, higher costs and more weight are the characteristics for the intermediate Green Roof type compared to that of the Extensive Green Roof.
A semi-intensive green roof includes a deeper substrate which allows for a greater range of landscape design options including grasses, herbaceous perennials and shrubs.
Intensive Green Roofs
Intensive green roofs have a deep growing medium that supports a wide variety of landscape design elements and plant types such as perennials, bushes and trees. Due to the a variety of design options the installation and maintenance costs are higher on an intensive green roof than on extensive or semi-intensive green roofs.