New green trends can quickly go from being virtually unknown to unavoidable.

Ten years ago, the term “green roof” would have likely conjured up images of paint colour, not a lush organic layer atop a building. Today, green roofs can be found on condos, office towers and factories across Canada.

As private developers and property owners learn more about the environmental and economic benefits of green roofs, they are being embraced as a sustainable and cost-saving measure. In this rapidly growing industry, Toronto has become a leader in promoting the installation of green roofs on new and existing developments.

In fact, according to Green Roofs for Healthy Cities’ founder and president, Steven Peck, the city’s green roof policies have surpassed all other Canadian municipalities’.

“Toronto has the most comprehensive green roof plan in North America,” he says. “The development industry in Toronto has embraced green roofing because it sees there are real tangible benefits, and that extends from big-box retailers to condominium developments.”

Peck adds there are also many public benefits of green roofs. They can save cities money by reducing stormwater runoff and lowering the urban heat island effect. He explains that these roofs essentially act as “air conditioning for the outdoors.”

And the benefits are not limited to the environment. Over the long-term, there can be real savings for private developers and property managers. Green roofs increase the life expectancy of a building’s waterproofing membrane, lower energy consumption and increase the attractiveness and, consequently, value of residential units.

Toronto’s leadership in the industry is due to the fact that green roofs are not only encouraged but, in some instances, are mandatory. On Jan. 31, 2010, the city’s green roof bylaw came into effect, making Toronto the first city in North America to enact a bylaw that requires the construction of green roofs on all new residential, commercial and institutional construction projects with a gross floor area of more than 2,000 square metres. It requires up to 60 per cent green roof coverage, with the size of the green roof dependent on available roof space.

The city defines available roof space as the total roof area excluding areas designated for renewable energy, private terraces and residential outdoor activity (to a maximum of two square metres per unit).

This means a smaller building with a gross floor area of 2,000 square metres only requires a green roof that covers 20 per cent of its roof space, whereas a larger building that is more than 20,000 square metres must have a green roof that comprises 60 per cent of its available roof space.

A similar green roof bylaw for industrial buildings came into effect April 30, 2012.

Jane Welsh, Toronto’s acting program manager of zoning bylaw and environmental planning, says the city’s rules surrounding green roofs are flexible. Developers can apply for a variance or exemption and, if approved, pay cash ($200 per square metre) in lieu of installing a green roof. The money accumulates in a fund for Toronto’s Eco-Roof Incentive Program, which was established to help existing buildings install green roofs on their properties.

In addition to strong bylaws, Toronto city staff have created educational documents and standards that are used by both private developers and cities throughout North America. A new resource, Guidelines for Biodiverse Green Roofs, provides best practices for promoting biodiversity on green roofs. It has been nominated for an Award of Excellence by the Canadian Society of Landscape Architects.

Peck says the green roof industry is growing fast and cities that promote green roofs are seeing the benefits through local job creation. One hundred million square feet of green roofing was created in North America over the last 10 years; Green Roofs for Healthy Cities projects the continent will reach one billion square feet within the next decade.

However, Peck says there are still some developers in North America that are skeptical about the benefits of green roofs and want to see them tested on other properties before investing. He argues that once they see that green roofs can save money in the long run, they will be more likely to voluntarily opt for one, though this is not always the case.

“There are some who will never adopt a green roof unless they have to,” he says.

Welsh says that in Toronto, where regulation is a key aspect of the green roof strategy, there is little push back from developers.

“There’s no questioning now,” she says. “It’s accepted as a cost of doing business.”

Daniel Viola is the online editor for Building Strategies & Sustainability and Canadian Property Management magazines. He is also the editor of Property Management Report.