Eco-Roof Incentive Program

The City of Toronto has embraced a program, beginning in 2006, of first encouraging, and later requiring, the use of green roofs or cool roofs in all new buildings constructed in the city. A green roof is one in which a soil substrate is installed on the rooftop, allowing for the growth of vegetation. The type and extent of the vegetation is related to the depth of the soil medium, with deeper soils providing enough support to allow for large bushes, and even trees, to grow. Cool roofs, on the other hand, do not have vegetation, but are covered in a highly reflective material that reflect solar radiation away from the building and helping to keep it cool. While there are many variations of green and cool roofs, both forms help to increase a community’s resilience to the effects of climate change by reducing urban heat islands, minimizing indoor overheating and reducing electricity consumption through lower air conditioning usage. In addition, green roofs provide the benefits of lower peak storm water volumes, increased biodiversity and habitat, and lower greenhouse gas emissions. Green roofs also provide valuable green space within dense urban environments where it otherwise would be limited.

Understanding and Assessing Impacts

The urban heat island effect is the idea that urban spaces will heat up more quickly, and to greater temperatures, than the surrounding countryside. A greatly simplified explanation is that the glass, steel, concrete, and asphalt (among other materials) will retain heat a greater amount of heat than a vegetated landscape would. One of the more pressing concerns in Southern Ontario regarding climate change is the predicted increase in extreme heat days, a factor that will only be exacerbated by the urban heat island effect. One of mechanisms that can be utilized to reduce the danger of extreme heat is the use of green or cool roofs, which use vegetated or reflective surfaces to help cool a rooftop and, therefore the building itself and the surrounding environs. Recognizing the continued growth and renewal of Toronto’s urban landscape represented an opportunity to build resilience as the city grew, the City of Toronto began looking into the possibility of a bylaw requiring the use of these roofs on all new construction and incentivizing green roofs and cool roofs on existing buildings. The City took into account many different variables when judging the efficacy of such approaches, including data on energy efficiency, storm water retention volumes, plant survival, unit cooling benefits and other variables. The use of these metrics indicated that such a program was financially viable.

Identifying Actions

The City of Toronto’s Eco-Roof Incentive program arose out of a multi-step process that carefully analyzed the implementation and consequences of increasing the use of green roofs and cool roofs in the city. The first step was taken, in 2003, was to create a controlled pilot program at a few select sites to determine the viability of the roof structure and experiment with planting different variations of vegetation species and communities to ensure optimal outcomes in both survivability and cooling (and other) outcomes. The first three selected sites were at Toronto City Hall, the Computer Science Building at York University, and the Eastview Neighbourhood Community Centre. Following the promising results from these tests, in 2005 the City of Toronto then commissioned researchers from Ryerson University to undertake an academic study investigation the various environmental, social, and economic costs and benefits of green roofs. The results of this study then encouraged the City of Toronto to implement the Green Roof Strategy in February of 2006. This strategy included measures to encourage widespread adoption of green roofs through the City’s development approvals process, education and outreach efforts, and, importantly, a financial incentive program. From 2006 through 2008, the City ran a Green Roof Pilot program with financial support for green roof projects to help showcase the viability of such designs. Following this, in 2009 the plan reached its final state by with the introduction of a mandatory Green Roof Bylaw and a supporting Eco-Roof Incentive Program.


The Pilot Green Roof Incentive Program, running from 2006-2008, was intended to facilitate the creation of pilot green roof projects that could be used as demonstration of the effectiveness, efficiency, and attractiveness of green and cool roofs in the city. This program was administered by Toronto Water, the City Division responsible for drinking water, wastewater, and storm water and was given a $200,000 budget for its two-year operation. The program provided rebates for the construction of green roofs of $10 per square meter, up to a maximum of $20,000. This program was open to all owners of private property across the City of Toronto. Following this pilot program, in 2009 the City enacted the Green Roof By Law requiring that all new commercial, institutional, and residential development with a roof space larger than 2,000 square metres be covered by a green roof. There exists some flexibility in the program, with total rooftop coverage ranging between 20% and 60% of total available roof space. Furthermore, the developer also has the option to make direct payments to the City in lieu of building a green roof – these payments help to support the ongoing incentive program. This incentive program, the Eco-Roof Incentive Program, also implemented in 2009, provides rebates for the construction of green roofs of $100 per square metre, up to a maximum of $100,000. Additionally, eligible cool roofs can receive $2 to $5 per square metre up to a maximum of $50,000. In order to be eligible for the rebate, green roofs must be constructed in accordance with the Ontario Building Code and the Green Roof Construction Standard.

Outcomes and Monitoring Progress

Since 2009, the Eco-Roof Incentive Program has supported 523 projects (93 green roofs and 430 cool roofs) with a total combined area of over 952,000 square metres of roof space; an area equal to about 117 football fields. In addition, these eco-roof installations are estimated by the City to have diverted over 16.8 million litres of storm water, reduced energy consumption by over 1,900 megawatt hours annually, and avoided over 356 tonnes of greenhouse gas emissions.