cityscape How Toronto Became a Hub for Green Roofs

Thanks to a City bylaw, they're popping up like weeds.

Few environmental successes are as pronounced yet absent from Torontonians’ daily awareness as our city’s embrace of green roofs. Maybe it’s because we can’t see them from our bar patio or yoga studio vantage points, but probably it’s because most roofs, green or grey, aren’t accessible to the public.

Green roofs have nevertheless become part of Toronto’s architectural DNA in a surprising array of applications. Countless condo and corporate buildings are adorned with foliage of all forms, high above the Big Smoke’s traffic jams. Though Victoria Park station’s green roof is only visible from nearby apartment buildings, commuters can at least catch a glimpse of Eglinton West station’s enormous rooftop garden on their north-south journey. There’s even a fully functioning farm on top of Ryerson University’s engineering building.

In 2015 Toronto installed the second-most square feet of green roofs in North America, only behind Washington, DC, according to the Annual Green Roof Industry Survey.

How did Hogtown mimic Gandalf’s transformation by going from Toronto the Grey to Toronto the Green Roof? Where is this young technology taking us? And, most importantly, why does it matter?

How we got here

There are approximately 500 green roofs, big and small, in Toronto. This is thanks to a 2010 bylaw [PDF] requiring all new developers to cover between 20 and 60 per cent of their buildings with vegetation. It’s the first (and, for now, only) regulation of its kind in North America, making Toronto uniquely positioned for environmental design.

The bylaw is why the 41-story RBC WaterPark Place [PDF] at Bay Street and Queens Quay has three green roofs that together could fill a NFL football field.

Developers can opt out of installing anything remotely grassy for a fee. But Jane Welsh, City Hall’s project manager for environmental planning, told Torontoist only five per cent of buildings choose to go sans-green roof.

Welsh also says municipally-owned buildings install a green roof anytime there’s a repair or replacement to the top of the building, when feasible.

That’s how four Toronto Public Library branches across the city—not including the new Albion branch or Wychwood branch extension—along with the two TTC stations and several community centres were outfitted with various shades of green. The Scarborough Civic Centre Library also has a green roof you can stroll beside on a walkway and was boosted by Susan Martin, TPL’s branch capital planning and implementation manager, as the TPL’s most publicly visible roof.

Where are green roofs going?

Solar panels have found a roof-mate.

According to one manufacturer [PDF], green roofs are purported to make solar panels more efficient and sturdy. Jelle Vonk, business manager of ZinCo Green Roof Systems, pointed to the company’s installation of a recycling centre in Brampton, which features more than 100 panels sitting atop a green roof, as one of the latest examples of the new eco-marriage.

Rooftop farming is another frontier. The Ryerson Urban Farm is Toronto’s only harvest well above ground-level, save for a few condo gardens; but Trent University’s rooftop farm in Peterborough, Ontario is also a nearby early adopter. Both yield impressive quantities of produce and illustrate a trend Vonk believes will take off, particularly with restaurants.

The future of elevated urban farming may lie in New York’s Brooklyn Grange, according to Jordan Richie of Green Roofs for Healthy Cities. Between just two roofs in New York City, the farms grow more than 50,000 pounds of organically cultivated produce every year. And, Richie says, it’s the only financially self-sustaining rooftop farm.

There are also urban habitats meant to provide birds with a more natural perch than statues or telephone wires and give bees a home away from your picnic. The habitats are built with a combination of vegetation or biodiversity, something Richie says is inherently more environmentally friendly. Varying heights of growth interspersed with logs makes urban habitat green roofs a classification of their own, Vonk says.

Why does it matter?

Keeping raw sewage out of Lake Ontario is partially why City Hall enacted its Green Roof Bylaw.

Toronto’s combined sewer system often overflows into the lake during rain or snow storms. Swimming in Lake Ontario is still sometimes not advised.

Green roofs absorb and retain rain water like a sponge, allowing the sewer system to cope when the skies open and the city is bombarded by whatever the season has in store.

It’s also about temperature. Toronto’s concrete absorbs heat and causes the whole city to turn up their AC, using more electricity and putting more stress on the already overheated environment. Green roofs cool down individual buildings and building clusters in an attempt to stop the warming cycle at its start.

But now green roofs are venturing down new utilitarian courses of renewable energy, urban farming, and natural conservancy—much to the city’s benefit.