Green Roof By-law For The City Of Toronto

In December of 2008, Toronto City Council adopted the Toronto Green Standard (formerly know as the Toronto Green Development Standard).  The Toronto Green Standard (TGS) is a set of performance measures for sustainable development that responds to the City’s environmental concerns.

This new standard is about designing buildings and landscapes that is more environmentally friendly.  The City believes that achieving the targets set out in the TGS will help to improve air and water quality, reduce green house gas emissions and enhance the natural environment.

Integrated into the TGS is the City’s Green Roof Strategy.  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 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.

In Ontario, uniform provincial standards for new construction are set out in the Ontario Building Code (OBC).  The province is responsible for code development and administration, while municipalities are responsible for enforcement.  Under the Ontario Building Code Act, the City cannot exceed the requirements of the code (which does not require green roofs) by requiring them in new construction.

Section 108 of the City of Toronto Act provides City Council with the authority to pass a by-law requiring and governing the construction of green roofs, as an “exception” to the Building Code Act, 1992, which generally prohibits municipal by-laws that exceed requirements under the OBC.

Section 108 of the Act also provides Toronto with a clear regulatory tool to implement Toronto’s Green Roof Strategy by not only permitting a city By-law to require green roofs but also to develop a green roof construction standard.

Green roofs are an emerging technology in North America, and as a result, there are currently no standards incorporated into Ontario’s OBC for the City to measure the design and construction of green roofs against.

The purpose of the Toronto Green Roof Construction Standard (TGRCS) is to provide requirements and recommendations that will allow a designer to design a green roof that will meet the City’s minimum requirements for green roof construction while also meeting the OBC requirements for the remainder of the building.

The TGRCS will also provide City staff with the technical foundation necessary for the development of a Toronto Green Roof By-law (TGRB) consistent with the City of Toronto Act.

The TGRCS will provide certainty and clarity for builders, contractors, developers, manufacturers and designers when designing and building green roofs in the City.

To assist City staff with the development of the TGRCS, a Green Roof Technical Advisory Group (TAG) was established with group members representing a diverse cross section of industry experts including a representative from the Ontario Industrial Roofing Contractors Association (OIRCA).

During this whole process the City undertook a coordinated public consultation with affected stakeholders.  These sessions provided an opportunity to address proposed thresholds, coverage’s, alternative compliance and transition provisions for requiring green roofs.

When enacted the TGRB would require green roofs on certain types of new buildings and regulate the design and construction of green roofs in Toronto.  Toronto would be the only municipality in North America to have a by-law of this nature.  The proposed TGRB will be an additional chapter to the Toronto Municipal Code.  Part A would contain provisions governing where green roofs would be required in the City.  Part B would contain the administrative provisions for governing the construction of green roofs.  The TGRCS itself would be a schedule to the By-law.

Building size and use characteristics will dictate the extent of green roof required.  Determining the size of the green roof area based on the building footprint ensures that the size of the green roof relates to the area contributing to the environmental impact of the building and that the size is not minimized through building design.

It is proposed that the By-law require an above grade green roof with minimum total area coverage as follows:

  a.  All residential development with a gross floor area (GFA) greater than 5,000 sq.m are required to install a green roof.
  b.  All Industrial, Commercial and Institutional (ICI) development with a GFA greater than 2,000 sq.m are required to install a green roof.
  c.  Any new development where there is more than one use in a single building, apply the threshold for the use with the largest GFA.
  d.  Size of the required green roof is determined by the GFA of a building  i.e. larger buildings require larger green roofs.
  e.  Green Roof coverage ranging from 20-50% of the footprint of the building (see table below).
  f.  GFA for affordable housing is exempt from the total GFA calculation.
        
Graduated Green Roof Coverage Requirements would be as follows:

          GFA                                      Coverage                        GFA                          Coverage

Residential: 5,000-9,999 sq.m          20%            ICI:    2,000-4,999 sq.m                    20%
10,000-14,999 sq.m                            30%                     5,000-6,999 sq.m                    30%
15,000-19,999 sq. m                           40%                      7,000-9,999 sq.m                    40%
20,000 sq.m or greater                       50%                     10,000 sq.m or greater             50%

                                    
For any industrial use development where the installation of a green roof is not technically practical or feasible the applicant may choose to implement the following alternative compliance for industrial buildings:

  •  Cool Roofing materials for 100% of available roof space; and
  •  Plant shade trees within car parking areas, at a minimum ratio of one tree planted for every five parking spaces supplied
  •  Plant shade trees at the equivalent of 6-8m intervals starting from the property line along all street frontages, open space frontages and public walkways, excluding driveways and easements; and

  •  A) Green* an area at grade or on the roof equivalent to the size of the required green roof
                                                              OR
     B) Retain rainwater from the roof for reuse up to and including the level of the 100 year storm, and Green* an area equivalent to 25% of the size of the green roof requirement.

* Green is defined as one or a combination of the following: a green roof, green wall, soft landscaping, shaded hardscape, open grid pavement, high-albedo surfacing materials.

The By-law will establish both the administrative framework and technical requirements that will govern green roof construction.  Included would be a permit system for anyone wishing to construct a green roof.  The TGRCS will establish criteria for all green roof system components, structural requirements, safety issues such as wind uplift and fire resistance, waterproofing best practices and vegetation performance.

The City of Toronto believes that the Toronto Green Roof By-law will place Toronto at the forefront of green roof implementation and design in North America.  The City plans to introduce the By-law in April of 2009.  It is expected to become effective for residential and commercial buildings in May of 2010 while industrial buildings will be required to comply after May 1, 2011. 

(The Ontario Roofing News wishes to thank the City of Toronto for providing background information for this article)

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