What You Need to Know
For the purposes of Toronto’s Green Roof Bylaw and the Eco-Roof Incentive Program, 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.
There are three main types of green roof systems:
- complete systems where all the different components including roof membrane are an integral part of the whole system
- modular systems that are positioned above the existing roofing system
- pre-cultivated vegetation blankets that consist of growing medium and plants that are rolled onto the existing roofing system with drainage mats and root barriers as required
Intensive or Extensive
Intensive/active green roofs have a deep growing medium that supports a variety of landscape design and growth. They are accessible and used as recreational space. An example of an intensive/active green roof is the Manulife Centre which is located over a parking garage. It is a well established green roof (25 years old) with mature trees that reach three stories high.
By contrast, an extensive green roof has a shallow growing medium and the landscaping is designed to be more self-sustaining, requiring less maintenance than an intensive system. Extensive green roofs are less expensive than intensive systems, since they are lighter and require less structural support and need less frequent maintenance. The roof on Mountain Equipment Co-op in Toronto is an example of an extensive green roof, built in 1998.
New or Retrofit
Green roofs can be designed to be an integral part of a new building, or can be installed later on an existing building. When a building is designed with a green roof system, there can be several benefits. For example, the building is designed to provide the necessary structural support, and won’t require reinforcement later. Also, the building can be designed to take advantage of the aesthetic value that a green roof can offer by providing viewing areas.
York University installed a 30,000 square foot green roof during the construction of the Computer Sciences Building in 2003. The green roof is not accessible. It has been monitored by the Toronto Region and Conservation Authority to determine the quantity and quality of stormwater and quantify other benefits of green roofs.
An example of a retrofit is the intensive 704m2 green roof on ESRI Canada Ltd. 12 Concorde Place. It covers 100% of available roof space on a commercial building, and it hosts 52 plant types including sedums, grasses, flowers, herbs, shrubs and trees.
Below is a brief description of a complete system that is more fully described in the consultant’s report, Environmental Benefits and Costs of Green Roof Technology for the City of Toronto.
In a complete green roof system, all parts of the roof are designed to support vegetation growth. These systems provide the most flexibility in terms of the type and nature of growing medium, drainage and protection layers and type of vegetation. Complete systems vary in thickness and weight from as low as 50mm to 75mm (2 to 3 inches) in depth and 60 to 90 kg per sq. m, (12 to 18 lbs per sq. ft.) in weight. They can be installed with a variety of waterproofing membrane types.
Below is a brief description of a modular system that is more fully described in the consultant’s report, Environmental Benefits and Costs of Green Roof Technology for the City of Toronto.
Modular systems are essentially trays of vegetation in a growing medium that are grown off-site and simply placed on the roof to achieve complete coverage. They are available in different depths of growing medium typically ranging from 75mm to 300mm (3 to 12 inches). The variety of vegetation is typically more limited.
Pre-Cultivated Vegetation Blanket
Below is a brief description of a vegetation blanket system that is more fully described in the consultant’s report, Environmental Benefits and Costs of Green Roof Technology for the City of Toronto.
A pre-cultivated vegetation blanket is a pre-grown interlocking green roof tile. The blanket shown below is available in a thickness of about 45mm (1.75 inches).
Photos courtesy of Elevated Landscape Technologies
Blanket systems are available in a variety of system designs. The most versatile system contains 25 mm (1 inch) of planting substrate. The result is a lightweight system ranging in weight from 40 to 60 kg per sq. metre.
The majority of the vegetation is made up of several varieties of sedum, a succulent plant (8.0 to 13.0lbs per sq. ft.) tolerant to extremes in temperature that survives with little or no irrigation while requiring very little maintenance. They are cultivated at ground level, then rolled and transported as a complete system on pallets or by crane.
Using Green Roofs to Enhance Biodiversity in the City of Toronto
Green roofs offer the potential to enhance biodiversity in urban areas such as Toronto. This report reviews literature on green roofs and biodiversity and examines opportunities to use green roof design templates, location and design strategies to enhance local biodiversity over time. This study expands on the 2004 study of green roof benefits by providing addition information on other citywide benefits of green roofs.
The Environmental Benefits and Costs of Green Roof Technology
Study of Benefits
In 2004, the City commissioned a team from Ryerson University to prepare a study on the potential environmental benefits of widespread implementation of green roofs to the City of Toronto, given the local environment and climate. The Study, titled The Environmental Benefits and Costs of Green Roof Technology, was undertaken with a grant from the Federation of Canadian Municipalities’ Green Municipal Funds, and in partnership with Earth and Environmental Technologies, one of five Ontario Centres for Excellence, supported by the Ontario Ministry of Economic Development and Trade. This Study 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 the energy use associated therewith).
The following are Reports on the Environmental Benefits and Costs of Green Roof Technology for the City of Toronto, prepared by Ryerson University:
- Full Report
- Executive Summary
- Table of Contents
- 1.0 About the study
- 2.0 Survey of research related to green roofs
- 3.0 Survey of types of green roofs and their standards
- 4.1 Description of approach
- 4.2.1 Use of geographic information system (GIS)
- 4.2.2 Costs of Green Roof Technology
- 4.2.3 Stormwater
- 4.2.4 Combined sewers
- 4.2.5 Air quality
- 4.2.6 Building energy and the urban heat island
- 5.0 Summary and recommendations
To determine the citywide benefits the study team calculated that approximately 5,000 hectares or 50 million m2 of roof area is available for green roofs in the City of Toronto. The study team also had to make some assumptions about the characteristics of the green roofs to be installed to calculate the citywide benefits.
The study assumed that green roofs:
- would be installed on roofs greater than 350 m2 in size
- would cover at least 75% of the roof area
- would be installed over heated spaces
- would be installed above grade (i.e. grade level roofs were excluded)
Although these assumptions exclude some conditions in which it is possible and beneficial to install green roofs, some basic assumptions were needed to find the total green roof area, in order to calculate the benefits. It is important to note that the conditions in the study are not the same conditions applying to the City’s green roof strategy.
The environmental benefits of green roofs are well documented, but have not been calculated on a citywide basis. Environmental benefits of green roofs in an urban setting include:
- Reduction in stormwater runoff that affects quality of local water resources which supply drinking water, are used for swimming, and serve as fish and wildlife habitat
- Reduction in energy consumption
- Reduction in the urban heat island effect and associated cooling costs
- Beautification of the City
- Creation of more natural green spaces
- Opportunities for local food production
- Reduction in stormwater flow of 12 million m3 per year
- Infrastructure savings worth between $2.8 and $79 million
- Erosion control measures savings worth $25 million
- Pollution control cost avoidance worth $14 million
- 3 additional “beach open” days per year worth $750,000
See the stormwater runoff results in the benefits study.
- Citywide savings from reduced energy for cooling is $21 million, equivalent to 4.15KWh/m2 per year
- Cost avoided due to reduced demand at peak times is $68 million
See the building energy results in the benefits study.
Urban Heat Island Effect
- Widespread greening of Toronto’s roof would reduce local ambient temperature from 0.5 to 2 degrees Celsius
- Citywide savings from reduced energy for cooling of $12 million, equivalent to 2.37 kWh/m2 per year
- Cost avoided due to reduced demand at peak times of $80 million
See the urban heat island results in the benefits study.
Air Quality & Emissions
- Reduction in levels of CO, NO2, O3, PM10, SO2
- Reduction in CO2emissions
See the air quality results in the benefits study.
Other Citywide Benefits
- Potential for local food production
- Habitat for birds and invertebrates
Building Level Benefits
- Energy savings from better solar reflectivity, evapotranspiration and insulation
- Green roofs last up to twice as long as regular roofs
- Green roofs can beautify and add value to Toronto’s buildings by
providing scenic views and recreational areas in dense urban areas
Q1. When will the Toronto Green Roof Construction Standard come into effect?
The Toronto Green Roof Construction Standard affects the design and construction of all green roofs under building permits applied for on or after January 31, 2010.
Q2. How do I apply for a building permit to construct a green roof?
As part of the Building Permit process for a Green Roof, Toronto Building staff must review your plans to ensure that they comply with the Toronto Green Roof Construction Standard, Ontario Building Code, local Zoning Bylaws and other Applicable Laws.
Toronto and East York District
Toronto City Hall
100 Queen Street West
14, 18, 19, 20, 21, 22, 27, 28, 29, 30, 31, 32
North York District
North York Civic Centre
5100 Yonge Street
8, 9, 10, 15, 16, 23, 24, 25, 26, 33, 34
Etobicoke York District
Etobicoke Civic Centre
2 Civic Centre Court
1, 2, 3, 4, 5, 6, 7, 11, 12, 13, 17
Scarborough Civic Centre
150 Borough Drive
35, 36, 37, 38, 39, 40, 41, 42, 43, 44
Q3. How much does a building permit for a green roof cost?
Building permit fees are set out in Chapter 363 of the Toronto Municipal Code and are based on a formula (service level index multiplied by area). The service level index (2009) for a building permit to construct a green roof is $4.82/m2. This fee will be adjusted annually consistent with other building permit fees.
Q4. Where can I get further information on the standard?
If you have further questions regarding development of the Toronto Green Roof Construction Standard, please contact Dylan Aster, Technical Advisor, Office of the Chief Building Official, Toronto Building, at (416) 338-5737 or email@example.com.
Whether constructing a green roof voluntarily, or as required by the Green Roof Bylaw, all green roofs in the City of Toronto, at a minimum, must conform to the Toronto Green Roof Construction Standard. The Standard can be found in Article IV of the Green Roof Bylaw (Municipal Code Chapter 492, Green Roofs). It complements the other sections of the Green Roof Bylaw which relate to definitions, coverage requirements, exemptions, and applications etc.
The purpose of the Toronto Green Roof Construction Standard is to govern the design and construction of green roofs by setting out minimum requirements that meet the City’s objectives and the Ontario Building Code requirements.
Mandatory provisions are included in the Toronto Green Roof Construction for the following areas:
- Green Roof Assembly
- Gravity Loads
- Slope Stability
- Parapet Height and /or Overflow Scupper Locations
- Wind Uplift
- Fire Safety
- Occupancy and Safety
- Water Retention
- Vegetation Performance
- Plant Selection
Green Roofs and Building Permits
As of January 31, 2010, the Toronto Green Construction Standard applies to all new building permit applications where a green roof is proposed.
There are no additional fees for a building permit to construct a green roof that is part of an application for a new building or an addition to an existing building. A separate fee is charged for a permit to construct a stand-alone green roof.
PAL/PPR Project Reviews
While not specific to green roof programs, these services can help identify at the pre-application stage whether a green roof may be required as part of a development construction project.
Green Roof Bylaw Screening Form
The Green Roof Bylaw Screening Form is a diagnostic tool to help determine whether the Green Roof Bylaw may apply to your application and if any proposed Green Roof meets the requirement of the Bylaw. The form is not required as part of a building permit or site plan application, but assists both applicants and city staff in reviewing the project.
Green Roof Designer Checklist
The Green Roof Designer Checklist is a voluntary tool to assist designers in reviewing green roof projects by providing a summary of Ontario Building Code and Green Roof By-law provisions. The form is not required as part of a building permit.
Green Roof Statistics Template
The Green Roof Statistics Template is required to be submitted for Site Plan Control Applications or Building Permit applications (where no site plan application is required) where a green roof is mandatory. The table must be completed and copied directly onto the Roof Plan submitted.
Green Roof Declaration Form
The Green Roof Declaration Form is required to be submitted for all new buildings or building additions applications with a gross floor Area exceeding 2000 m², or where a green roof is proposed to be constructed.
Green Roof Inspection Report – Checklist
The Inspection Report Checklist is required to be submitted upon completion of the installation of the green roof to verify that the installation conforms to the Toronto Green Roof Construction Standard: Mandatory Provisions.
For additional information on how the Toronto Green Roof Construction Standard may apply to your project, please contact the Toronto Building Customer Service Counter closest to you.
For additional information on how the Toronto Green Roof Construction Standard may apply to your project, please contact the Toronto Building Customer Service Counter closest to you.
Toronto Green Roof Construction Standard: Supplementary Guidelines
Toronto Building has prepared a guideline document to the green roof construction standard, in consultation with the City’s Green Roof Technical Advisory Group. The document contains “best practices” in green roof design, provides designers and the public with additional information on the Toronto Green Roof Construction Standard and contains illustrations to assist with calculating required green roof coverage.
For general information on the Toronto Green Roof Construction Standard, please contact Dylan Aster, Technical Advisor, Office of the Chief Building Official, Toronto Building, at 416-338-5737 or firstname.lastname@example.org.
Design Guidelines for Biodiverse Green Roofs identify, describe and illustrate best practices for creating habitat and promoting biodiversity on green roofs in Toronto.
Toronto is the first City in North America to have a bylaw to require and govern the construction of green roofs on new development. It was adopted by Toronto City Council in May 2009, under the authority of Section 108 of the City of Toronto Act.
The Bylaw applies to new building permit applications for residential, commercial and institutional development made after January 31, 2010 and will apply to new industrial development as of April 30, 2012.
- Green Roof Bylaw (Toronto Municipal Code Chapter 492, Green Roof)
which is to be read together with the following amendments:
Am I required to build a green roof?
The Bylaw requires green roofs on new commercial, institutional and residential development with a minimum Gross Floor Area of 2,000m2 as of January 31, 2010. Starting April 30, 2012, the Bylaw will require compliance with the Bylaw for new industrial development. Use the green roof screening form as a tool to determine quickly whether you will be required to build a green roof. Details of the requirements are provided below. The green roof coverage requirement is graduated, depending on the size of the building. The table below shows how the requirement ranges from 20-60 per cent of Available Roof Space for commercial, institutional and residential development. Available Roof Space is defined as the total roof area minus areas designated for renewable energy, private terraces and residential outdoor amenity space (to a maximum of 2m2/unit). A tower roof on a building with a floor plate less than 750m2 is also excluded from available roof space.
|Gross Floor Area *
(Size of Building)
|Coverage of Available Roof Space
(Size of Green Roof)
|2,000 – 4,999 m2||20%|
|20,000 m2 or greater||60%|
* Note: Residential buildings less than 6 storeys or 20m in height are exempt from being required to have a green roof.
The Green Roof Bylaw applies to new building permit applications for industrial buildings or additions to industrial buildings where the Gross Floor area is 2,000 m2 or greater and the application was made on or after April 30, 2012. Under the Green Roof Bylaw, Industrial buildings are required to provide one of the following:
- a Green Roof covering the lesser of 10 per cent of Available Roof Space or 2,000 m2; or
- a roof that uses Cool Roofing Materials for 100% of the Available Roof Space and complies with the stormwater management performance measures required through the Site Plan Approval process. Where the Site Plan Approval is not required, the first 5 mm from each rainfall or 50% of annual rainfall volume falling on the roof is retained or collected for re-use at least through systems that incorporate roof surfaces.
For all development where a green roof is required under the Bylaw, the applicant may apply for a Variance or an Exemption where the requirement is not met. A Variance allows a smaller amount of green roof than is required under the Bylaw, provided that a cash-in-lieu payment of $200/m2 is made for the reduced green roof area, and the application is approved by the Chief Planner. An Exemption from the green roof requirement is necessary when a green roof is not proposed for a development. An Exemption requires the approval of the Chief Planner and a cash-in-lieu payment of $200/m2 if the application is approved. Contact the Community Planner assigned to your application for further details on the Green Roof Bylaw Variance or Exemption process.
To determine quickly whether you will be required to build a green roof and the size of green roof that must be provided, use the Green Roof Screening Form as a tool.
For new development requiring Site Plan Approval, green roof statistics should be provided with the Site Plan application to facilitate compliance with the Green Roof Bylaw at the time of Building Permit Application. Complete the template for the Green Roof Statistics and copy it onto the Roof Plan submitted as part of any Site Plan Control application or Building Permit application. For associated Building Permit Applications, complete the Green Roof Declaration Form.
For new development requiring a Building Permit only complete the required Green Roof Declaration Form for submission at the time of Building Permit Application.
This template is required to be submitted for all Site Plan Control or Building Permit applications where a green roof is required under the City of Toronto Green Roof Bylaw. Complete the table and copy it directly onto the Roof Plan submitted as part of any Site Plan Control Application requiring a green roof in accordance with the Bylaw.
- Green Roof Bylaw Screening Form
- Building Permit Resources for Green Roofs
- Native Plant Suggestions – suggested indigenous plants for a Green Roof environment in Toronto developed by the Toronto and Region Conservation Authority.
- City Council decision to amend the Green Roof Bylaw for industrial buildings (November 29, 2011)
- City Council Decision to extend Industrial building exemption (February 7, 2011)
- City Council decision to adopt the Green Roof Bylaw
(May 25-26, 2009)
Background Information Reports
- Green Roof By-law Staff Report (March 27, 2009)
- Supplementary report from the Chief Planner and Executive Director, City Planning and the Chief Building Official and Executive Director, Toronto Building (May 22, 2009) (PG25.3d)
- Supplementary report from the Medical Officer of Health (May 22, 2009) (PG.3e)