The concept of a ‘green roof’ — a roof that is partially or completely covered with vegetation — has been around for centuries, but increasingly, cities are looking at how green roofs can be used to mitigate a variety of issues, from hunger to energy demand to the impacts of climate change.

“Green roofs are one of those rare technologies that have so many different benefits, depending on who’s adopting the green roof and the outcome they’re looking for.” says Greg Yuristy, general manager of Wellington, Ontario-based Smart Green Technologies. “The more places we can put vegetation, the better.”

In 2009, Toronto became the first city in North America to pass a bylaw requiring all new construction with a footprint of more than 2,000 square meters to incorporate a green roof. The move was primarily intended to reduce the strain on the city’s aging sewer system (studies have found green roofs can retain 60 to 100 per cent of incoming rainfall depending on their substrate depth), but the roofs also help to naturally cool and freshen the air on hot summer days, reducing electricity demand. Some even provide space for recreation and food production.

Here are five green roofs in Toronto and beyond that are stretching our conceptions of where vegetation can thrive and what that means for city life:

Rye’s HomeGrown – Toronto, Ont.
Ryerson University initially installed a green roof on its engineering building in 2004 to reduce building energy costs, but since 2013, Rye’s HomeGrown, an organization of students and faculty dedicated to creating a closed-loop food supply system on campus, has converted some 10,000 square feet of the rooftop into fruit and vegetable gardens. Produce grown on the roof is sold at Ryerson’s weekly farmer’s market and to campus food services, and the profits are reinvested into maintaining and expanding the gardens.

Seaport Farmers’ Market – Halifax, N.S.
The Halifax Seaport Farmers’ Market was developed to serve the city’s growing cruise ship tourism industry, but it’s also an ecological showcase. Its green roof, which can be admired from a full-length rooftop deck with a view of the ocean, helps cool the building in summer, while four small rooftop wind turbines generate electricity. Water for the public washrooms is heated by the sun.

Fairmont Waterfront Hotel — Vancouver, B.C.
Everything at the Fairmont Waterfront Hotel, from its menu to its electric vehicle charging stations, is designed with sustainability in mind. Its 2,100 square foot rooftop garden, planted in 1995, was one of the first green roofs in Canada and grows herbs and produce for use in the hotel restaurant. The roof is also home to an apiary for honeybees and habitat for solitary bees.

Rio Tinto Alcan Planetarium – Montreal, Que.
Designed by architects Cardin Ramirez Julien and difica Architecture + Design, the Rio Tinto Alcan Planetarium in Montreal’s recently-overhauled Olympic Park is an example of how vegetation and construction can be seamlessly interwoven to improve the appearance and efficiency of buildings. An accessible green roof connects the different levels of the building, providing space for the public to walk and rest, while two massive rainwater reservoirs collect runoff to irrigate the roof and supply water for the public washrooms.

Vancouver Convention Centre – Vancouver, B.C.
At six acres, the green roof that covers the West Building of the downtown Vancouver Convention Centre is the largest in Canada and the largest non-industrial vegetative roof in North America. The roof features more than 400,000 native plants and grasses that provide insulation and habitat for pollinators.