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TO: |
Mayor and Members of Council |
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FROM: |
Stuart Taylor, Director, Strategic
Services |
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PREPARED BY: |
Victoria McGrath, Manager,
Environmental Leadership |
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DATE OF MEETING: |
2003-Oct-20 |
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SUBJECT: |
Green
Roof Feasibility Study |
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RECOMMENDATION:
That the staff report entitled “Green Roof
Feasibility Study Results”, dated October 20, 2003, be received.
And, that funding for implementing an extensive green roof system at the Civic Centre roof that allows public access on the lower level be included as a 2004 capital submission for consideration during the budget process.
PURPOSE:
The purpose of this report is to present the
results of the Green Roof Feasibility Study and to outline the steps necessary
to install a green roof on the Civic Centre.
BACKGROUND:
Each
year, members of the Greater Toronto Area Clean Air Council, including Markham,
are asked to make commitments to improve air quality in the Greater Toronto
airshed. These commitments are included
in the Intergovernmental Declaration on Clean Air that is signed at the annual
Smog Summit. In June 2002, at the City
of Toronto Smog Summit, the Town of Markham committed to implementing a green
roof on the Civic Centre. The
commitment to implement a green roof at the Civic Centre came from a
recommendation by the Town of Markham’s Clean Air Working Group, comprised of
members of council and staff.
In
April 2003, Clarifica Water Resources Engineering submitted to the Clean Air
Working Group a feasibility study proposal on behalf of a Green Roof Consortium
comprised of not-for-profit public and private organizations including the
Toronto and Region Conservation Authority, Seneca College and Ryerson
University. The feasibility proposal
outlined how a green roof could improve storm water quantity and quality,
moderate temperatures, improve air quality and potentially reduce water consumption
in the Civic Centre pond.
OPTIONS/DISCUSSION:
What is a green roof?
A green roof is a green space created by adding layers of growing medium and plants on top of a traditional roofing system. There are two basic types of green roofs, intensive and extensive. Intensive roofs are characterized by increased weight and capital costs, intensive plantings and higher maintenance requirements. Because of their weight, intensive roofs can often be publicly accessible because the load-bearing capacity of the roof is sufficient to bear the weight of the “garden”. Extensive green roofs are characterized by low weight, low capital cost and low maintenance; however, extensive roofs are often inaccessible due to the low load-carrying capacity of the roof structure.
Green roof infrastructure provides a range of social, economic and environmental benefits. The Civic Centre Green Roof initiative is an excellent opportunity for the Town of Markham to demonstrate environmental leadership, particularly within the Markham Centre planning area. As a demonstration site, the green roof could showcase multiple local, regional and global benefits including:
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Storm water quality and quantity benefits
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Energy efficiency through moderating
temperatures
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Reducing the urban “heat island” effect
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Improving air quality including filtering
pollution and reduced greenhouse gas emissions
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“Stepping stone” wildlife habitat, helping to
connect isolated natural areas
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Public education and interpretation
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Aesthetics and quality of life
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Recreation and relaxation for Council members
and staff
In
addition, as the Markham Centre project moves forward, green roofs could be
considered in the design of the buildings and parking areas. Green roofs could supplement natural areas
in locations, such as Markham Centre, where intensification is desired.
Other
local examples of green roofs
There are several buildings with green roofs within the Toronto area, including:
§ Toronto City Hall where a small series of publicly accessible intensive and extensive roof gardens have been established;
§ Eastview Community Centre in Toronto has an extensive, publicly inaccessible green roof;
§ Mountain Equipment Co-op, Toronto has an extensive green roof, and;
§ York University’s Environmental Science building, where an inaccessible extensive green roof system has been installed.
There are additional examples of green roofs in different stages including Humber College, where a green roof system is being developed around the arboretum and another green roof in the City of Waterloo.
How
is a green roof “planted”?
Green roof development involves the creation of “contained” green space on top of a human-made structure. This green space could be below, at or above grade, but in all cases the plants are not planted in the ground. The Town of Markham Civic Centre already has a partial green roof over its parking garage (see Appendix A, diagram of existing garage). This can be incorporated into the design for the green roof on the Civic Centre building itself.
The green roof proposed for the Civic Centre roof is applied as another layer on the roofing system. The green roof layering technology includes:
§ The roof structure and insulation
§ A waterproof membrane, with a root-repellant membrane placed on top
§ A drainage layer, with built-in water reservoirs
§ A landscape or filter cloth to contain the roots and the growing medium
§ A specialized growing medium that does not include soil
§ Plants
For a diagram illustrating the layering technology of a green roof, see Appendix B.
During the Phase III replacement of the roof membrane on the upper roof level, starting in July 2003 and still currently taking place, a root repellant membrane was added in anticipation that a green roof would be created at the Civic Centre (see Appendix C, Area of Flam Jardin Membrane). The root repellant membrane was applied in sections to ensure that mechanical outlets on the roof remained unimpeded and these areas are now ready for the additional layering technologies.
Maintenance
of the Green Roof
The green roof system on the Civic Centre will require regular maintenance, including fertilizing, maintaining the irrigation system, replacing dead plant material and general tidying. Maintenance will be an important part of keeping the green roof attractive for the public, staff and members of council.
Maintenance will also be important to monitor the attractiveness of the green roof to the Canada goose population at the Civic Centre. Canada geese generally prefer nesting habitat that allows them to walk significant distances during the period of moulting that occurs after the eggs have hatched. During this time, usually three weeks, geese do not fly which would leave them “stranded” on the Civic Centre roof, which may make it unattractive for nesting. Plant species will be selected that are not attractive to geese, however it is possible that geese will find the green roof attractive for nesting.
Consideration of the environment is a significant component of Communities in Bloom. A green roof at the Civic Centre would demonstrate the Town’s commitment to the environment and provide an environmental gateway to the community and Markham Centre. In addition, having a green roof at the Civic Centre in time for Markham’s participation in Communities in Bloom would provide an example to other businesses in the community and encourage the implementation of green roofs within Markham.
In
order to determine if it was possible, structurally, to install a green roof on
the Civic Centre, a feasibility study was undertaken in July 2003. The scope of
the feasibility study included technical reviews, conceptual modifications,
concept drawings, monitoring, cost estimates and documentation (see Appendix
D).
The
results of the feasibility study demonstrate that an extensive green roof with
public access is possible, structurally, on the south wing roof (Phase 1 of
roof replacement, see Appendix E) of the Civic Centre and an inaccessible
extensive green roof is possible on the third floor roof (Phase 3 of roof
replacement, see Appendix E). The feasibility study also includes how the Town
could incorporate monitoring equipment into the green roof system to measure
temperature and storm water quality and quantity.
As
part of the feasibility study, a landscape architect prepared concept plans for
a green roof at the Civic Centre (see Appendix F). The concept plans illustrate
a green roof system and includes enhanced public education and interpretation
opportunities to showcase the green roof as a gateway to Markham and Markham
Centre. It must be recognized that the enhanced concept includes structures and
plantings that will require additional structural capacity on the Civic Centre
roof and this is not recommended at this time.
Increasing structural capacity on the Civic Centre roof would require
construction and substantial disruption to internal workspace.
In
order to proceed with implementation of a green roof, detailed design including
plant species and locations, monitoring specifications and construction details
would need to occur.
FINANCIAL CONSIDERATIONS:
Funding
for implementing an extensive green roof system at the Civic Centre roof will
be included as a 2004 capital submission for consideration during the budget
process. It is expected that
implementing the green roof system at the Civic Centre will cost $500,00.00,
which could be phased over a number of years.
BUSINESS UNITS CONSULTED AND AFFECTED:
Community
and Fire Services Commission
ATTACHMENTS:
Appendix A - Diagram of Civic Centre parking garage
Appendix B - Layering technology of a green roof
Appendix
C – Flam Jardin on Phase III replacement
Appendix
D - Feasibility study
Appendix
E - Phase 1 and 3 of roof replacement
Appendix
F - Concept plans for a green roof at the Civic Centre
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Stuart Taylor, Director, Strategic Services |
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Jim Sales, Commissioner, Community and Fire
Services |
