Canada: A Leader in Green Roofing?
More than a passing environmental trend, green roofs are here to stay
By JOY SCHMIDT, President, Xero Flor Canada

If you had a bird’s eye view of some cities, you’d probably be astounded by all the fields of green, yellow, orange, red and pink growing way up into the sky. Dotted with pastures and meadows, and the occasional bushes and trees, barren rooftops across the country are going green. Up until recently, the growth of green rooftops across the continent was based on a designer’s sensibility and the willingness of property owners to catch the sustainability wave. Now, several municipalities across North America have moved to legislate green design, and more specifically green roofs, as a solution to growing urban environmental concerns.

While green roofs have been used extensively in parts of Europe for decades, it is only in the last few years that North American cities have developed green roof policies, incentives and legislation. According to the U.S. Energy Information Administration, the built environment respresents the largest source of greenhouse gas emissions and energy consumption in the world. American cities such as Portland, Chicago and Atlanta see living roofs on the deserted urban roofscapes as an answer. With their eco-policies and incentives they’ve been touted as leaders in green roofs in recent years. That was until May 2009, when Toronto City Council passed the most comprehensive green roof by-law and construction standards on the continent. The mandatory rooftop greening applies to residential buildings of six stories or more, and buildings with a gross floor area over 2000m(2). The Toronto by-law requires up to 50 per cent green roof coverage on multi-unit residential buildings, on schools, non-profit housing, and commercial and industrial buildings. Toronto’s landmark green roof by-law is now compared to others in Germany, Austria, Switzerland and Japan. Countries as far away as Australia are showing keen interest and looking to Toronto as a model for their cities.

Green Roof By-Laws and Incentives in Canada
Sustainable Roofing Lowers Energy Costs, Advances Environmental Goals
While it catapults green roof construction to another level, Toronto’s by-law isn’t Canada’s first. Other Canadian cities have enacted green roof legislation in recent years. Port Coquitlam, BC, became Canada’s first with a by-law in 2006 requiring green roofs for all buildings greater than 5000 m2 (53,821 sq. ft.). Also in BC, the City of Richmond recently enacted legislation requiring all new buildings greater than 2000 m2 to green 75 per cent of their roof or obtain a LEED Silver Rating equivalency for the building. Vancouver, Winnipeg, Waterloo are all greening their municipal rooftops and officials are encouraging builders to take it city-wide. Durham Region, just east of Toronto, Ont., and other cities require builders to meet the Leadership in Energy and Environmental Design or LEED green building rating system for new construction, with green roofs providing significant credits.

There are many municipalities, including Toronto, that are providing incentive programs and grants to encourage the installation of green roofs to achieve the overall benefits. Following the short-term pilot program where 46 projects received funding in Toronto in 2006 and 2007, the city’s new Eco-Roof Incentive Program will award $2.6 million over five years to successful applicants. The program’s target is to green 10 per cent of Toronto’s ICI roofs by 2020 to mitigate the urban heat island effect and stormwater concerns, among other things. The program will target building retrofits in the downtown core and new, large ICI buildings citywide. The city will grant $50 per square metre of green roof installed up to a maximum of $100,000 per award.

Green Roof Concerns: Do it right the first time
Use Technology That’s Tried and Tested
Whichever way you slice it, green roofs have arrived, and are here to stay. As in all construction, there are proper ways to go about it. And, there are ways not to. Green Roof installations are most easily applied on flat rooftops although applications can generally be placed on sloped rooftops. Although there are few green roof standards to guide roofers and builders, millions of square metres of various green roofs have been installed all over Canada on industrial, commercial, residential, institutional and educational buildings. Some have been more successful than others. Without standards, the onus is on designers and installers to be aware of best practices and do their homework. The success of your green roof will depend on your own due diligence. Proper planning and design, coupled with proven technology, will ensure a failsafe green roof on almost any building with various roof slopes. In addition to choosing trained professionals to ensure proper installation, it is integral to choose the right green roof system and technology for your building with considerations for the local climate.

To some North American roofers and builders, green roofs are still a peculiar and new phenomenon. ‘What? Vegetation growing on the roofs?’ one roofer recently asked. Yet, modern green roof technology has existed in Europe for nearly 40 years and continues to advance the industry worldwide. This technology is being adapted for North America’s climate and includes systems such as the pre-cultivated vegetation mats. The mat system was used on the Ford Assembly Plant retrofit in Michigan, which now stands as the world’s largest green roof at 10.4 acres. One of the advantages of such a system is easy installation and cost effectiveness. A first time installer in Toronto, Peter Liu, recently reported, “It’s very similar to laying down sod but the plants are drought tolerant and they flower.”

Green Roof 101: What is a Green Roof?
Basic Green Roof Components
Green roofs have been developed to replace the green space destroyed during the construction of the building, thereby mitigating the building’s environmental footprint. There are many green roof systems to choose from which affect water retention levels, saturated weight and LEED points, to name a few. The basic components of a green roof consist of the root barrier, a drainage layer, filter fabric, growing medium and plants.

Green roofs are either ‘intensive’ or ‘extensive’ depending on the vegetation and usage of the roof. Intensive green roofs use a wide variety of plant species that may include trees and shurbs, require a deeper growing medium, more maintenance, and are often park-like areas accessible to the public. In contrast, extensive roofs consist of herbs, grasses, mosses, and drought tolerant succulents such as sedum, which require minimal maintenance and can be sustained in a shallow substrate layer of two centimetres (1.5 inches). Some building owners are starting to use green roof space for urban agriculture growing herbs, fruits and vegetables.

The cost of green roofs vary depending on the design, roof access and project scale. An extensive green roof could cost $100 to $160 per sq. metre installed ($10 to $15 per sq. foot installed).

The primary barrier to green roofs in North America has been, in part, a lack of understanding of the technology and also the greater initial cost over a conventional roof system. Yet, the savings related to doubling the roof’s lifespan as well as the energy cost savings, as well as the environmental benefits, make a green roof part of the economic solution in the long term. As public understanding grows, more people are catching the green wave overlooking our cityscapes high above.

Harbingers of Green Roof Success & Safety:
Engineered Soil Mix, Quality of Material & Proper Installation
The engineered soil mix is critical in determining the long-term success of the living roof. It is important to note that the conditions of growing a green roof are harsher than growing a garden at ground level. The soil mix for a green roof needs to be permeable and have positive drainage but, at the same time, retain a certain amount of water retention for plant survival. The right soil mix is also one of the key factors in preventing green roof fires. Organic matter burns more easily. The ratio of organic matter to mineral mix is very important. Stone ballasts, or vegetation-free zones, at the perimeter and around any structure on the roof, act as a fire-stop and are recommended, in some cases required. Check with your local municipality and building code. If you have a green roof that is not irrigated, extra precautions such as watering during extended drought need to be taken. A successful green roof depends on the right soil mix, the right plant selection and the maintenance. Together, these play a vital role in fire safety.

Wind is another consideration on rooftops. Measures need to be taken to prevent wind uplift and soil erosion. The German FLL have green roof guidelines when it comes to fire and wind safety. Tests have been done on thin-layered extensive systems against fire and wind uplift. Proven technology is out there. Do your homework and ask the right questioins to ensure long-term success. Ultimately, it is advisable to go to a single supplier. Find a manufacturer and supplier who conforms to the FLL, and provides a warranty for materials and workmanship.

Leaks?
Concerned about leaks? Leaks are caused by defects in the waterproofing layer. The Green roof is a separate system sitting above the waterproofing layer. Installers need to take great care not to damage the waterproofing layer. “Green roofs do not cause leaks,” says Dr. Karen Liu, director of Research and Development, Xero Flor International, who authored many scientific studies on green roofs. “On the contrary, Green roof shields the waterproofing from harmful ultra violet rays and daily temperature cycling, and thus help to extend the roof’s service life.”

Leak detection is recommended before and after green roof installation as leaks can be difficult to detect and costly to repair. Electric Gradient Leak Locate is one of the non-destructive techniques that can pinpoint leaks in the waterproofing layer under the green roof.

Retrofits
Many existing buildings in urban centres want the additional green roof space as an attraction for their occupants. For existing buildings, extensive green roofs are generally more feasible due to their light weight. The saturated weight of many extensive systems ranges from 43 to 73 kilograms per sq. metre (eight- to 15-pounds per sq. foot). This lightweight system allows it to be placed on existing roofs with little or no structural modifications. However, retrofits must always start with a structural assessment to determine the load capacity.

Whether it be new construction or retrofit of existing buildings, with green roofs we will all win. With restored habitats, perhaps some of those birds and other creatures that have abandoned visiting our urban centres will choose to drop by. Many of the benefits of greening our skyline will only be known in the years to come.

About the Author
Joy Schmidt, president of Xero Flor Canada oversaw many international projects while working at Xero Floor’s German headquarters, and was instrumental in realizing the largest green roof in the world – a 10.4-acre extensive green roof on Ford Motor Company’s Rouge Assembly Plant in Dearborn, Mich. Under Joy’s leadership, Xero Flor Canada has successfully installed green roofs in five provinces across Canada. Xero Flor is also contributing to the development of green roof standards as well as to university research in Canada and the United States. Due to great interest, Xero Flor is conducting green roof workshops across Canada for roofers, specifiers, architects, etc. For more information and to register, write to This e-mail address is being protected from spam bots, you need JavaScript enabled to view it or www.xeroflor.ca.