Photo: Green Roofs for Healthy Cities.

Green roofs have become more than a trend over the past decade. Municipalities around the world have chosen to adopt bylaws requiring green roof installation in new commercial builds. Although green initiatives, in general, are still contentious due to initial costs, research has borne out the long-term benefits of green roofs for municipalities, the building’s users, and building owners.

The benefits of green roofs

Lower Energy Costs and Prolong the Life of the Vapour Membrane

According to information published by the National Research Council of Canada, an extensive green roof could reduce heat flow into the building by 75%, thus saving owners on air conditioning costs during warmer months of the year.

“There’s a lot of science behind green roofs,” said Costa Pavlou, principal and contractor at Toronto-based SKYSPACE Green Roofs. “There’s a lot of purpose and function.”

The extra layers on the roof’s surface go farther than providing an insular effect. They actually act as a UV barrier that protects the roofing membrane, prolonging its life from an average 15 years to 70 years or more.  

Green Spaces Could Mean Improved Moods and Faster Healing

The social impacts of green roofs are harder to measure, but some studies have undertaken to do just that. Employers have started to include amenity decks in their new builds as they can affect employees’ happiness and productivity. Meanwhile, hospitals are installing healing gardens, complete with shade trees and benches, because patients are known to heal faster when looking at a vegetative landscape.

Improve Drainage and Heat Quotients in Urban Areas

While naysayers still dismiss green roofs as a greenwashing ploy, municipalities have good reasons to implement green roof rules. Rain runoff from buildings creates an overload in cities’ sewer systems. However, a correctly installed green roof captures the water and slows down its release into the drainage system. 

“It’s a stormwater management tool,” Pavlou said. “There’s a paradigm shift. There was a time that we wanted water off the building as fast as we could, with no pooling water. Now, because of technology, we want to keep it on the building and delay its outflow.”

As global temperatures rise, buildings, pavement, and sidewalks capture the sun’s heat and store it, further increasing cities’ overall temperatures. This phenomenon, called a ‘heat island,’ makes residents hotter and increases energy use. Green roofs actually stop the heat buildup and lower cities’ ambient temperature during the warmer months of the year.

Especially Inventive Green Roofs

A green roof’s benefits go beyond these immediately measurable markers, as owners take the idea and make it their own. For instance, in 2017, an IGA grocery store in Montreal set up a 25,000 square-foot garden roof on the top of the building. It grew organic food, which was then sold in the store below, providing fresh, healthy food to its patrons. The IGA’s owners went a step further to spell out their store’s name in the rooftop garden’s design, thus getting an overhead marketing boost.

In 2018, The Teck Acute Care Centre at the BC Children’s and Women’s Hospital in Vancouver won a Green Roofs for Healthy Cities Award of Excellence for its use of the rooftop real estate as a healing area for patients. Teck’s green roofs mirror those of the BC landscape. Greenery on outdoor spaces located on lower floors mimics a forest floor ecosystem, while the highest roof decks resemble mountaintop meadows.

Green Roof Bylaws

Many municipalities in North America have enacted green roof bylaws, requiring green roofs on new commercial, industrial, or sometimes even multi-dwelling builds. Toronto, Washington, and Portland are a few examples. Builders don’t always welcome the requirement. Most recently, some builders in Gatineau have appealed a bylaw passed in January 2020, claiming the added costs associated with including green roofs on new builds will drive developers out of the community and into nearby cities.

Steven Peck, founder of Green Roofs for Healthy Cities, believes arguments that pit environmental technology against economic success are really outdated. 

“That’s antiquated talk,” Peck argues. Building owners, municipalities, and city dwellers will reap both economic and social benefits thanks to the implementation of environmental technologies. “It’s a win-win because building owners get benefits as well. It has the potential to be a positive on their bottom line.

“We need to prepare and look at roofs as infrastructure and plants as infrastructure,” Peck said. “There are a lot of negatives that go away when you implement a green roof on a structure, and the public bears many of those negatives.”

According to Peck, cities that adopt these policies will weather the effects of climate change best. “It’s a positive from an investment point of view.”

Pavlou points out people are catching on. Even owners not affected by green roof bylaws consider installing them, as are owners of existing buildings. Those not mandated to install a green roof are sometimes eligible for grant money. Some very lightweight systems suitable for buildings of all types are available, Pavlou said.