What About Those Green Roofs?

Wasn’t there supposed to be an explosion in green roofs? I Googled “green roofs Toronto” and the most recent return was a Globe & Mail article dated July 23, 2012, when there were about 135 green roofs afoot in the city. There were a couple of more recent entries farther down the list (although they contained nothing new), but the dearth of articles espousing the greatness of green roofs would seem to indicate that they’ve largely fallen off our radar. I got more responses to the query, “Why aren’t Toronto developers building more green roofs?”

Their benefits include the reduction of energy required for heating and cooling, which is certainly a good thing for residents. Unfortunately, the urban farming that pops into many people’s minds when they think of green roofs — a place for residents to lovingly tend gardens and provide fresh fruits and vegetables to city dwellers — isn’t practicable, and wasn’t on the minds of those who pen the bylaws.

The bylaws apply to new developments of more than six storeys with a gross floor area of 2,000 square metres or more, and require 60 percent of the surface area to be green. That means the vast majority of new condos being built in the city should have green roofs. They contain no prohibitions for what kinds of plants may be grown, except noxious weeds; however, construction rules requiring that plants cover 80 percent of a green roof by year three effectively prohibit most food plants. That’s because most of the vegetables we grow are harvested and replanted throughout the fair weather season, then die with the frost. A fallow green roof isn’t very green.

At Ryerson University, an urban agriculture student group in 2013 successfully applied for garden expansion and deeper soil for the roof of its engineering building. Over a two-year experiment, they produced more than 2,500 kg of food. It was originally built before the city bylaws, and wouldn’t be permitted now.

It’s another dichotomy between the real world and bureaucracy that is undermining what gets residents excited about green roofs. Water run-off, on the other hand, doesn’t excite anyone except a few very nerdy city officials.

“City bylaws are designed to mitigate city concerns,” points out Toronto roofer Brian Steen. “It’s about cost mitigation because they have to deal with overflow. If you have 2,000 square metres of concrete roof, every drop runs off and into the sewers all at the same time. Green roofs delay all that water anywhere from say 90 minutes to three hours or so. It doesn’t negate the other benefits, but urban agriculture was never what green roofing was about for administrators.”

Zigg Rooftop - by Fieldgate and Madison Homes

While the rift between those who make the rules and those passionate planters who must abide by them is real, it may not matter for long. While it’s possible that there’s an answer to the problem of fallow roofs that still allows for food production, Steen says he thinks green roofing technology, like automotive technology, simply advances too quickly for the bylaws anyway.

“I suspect that, like hydrogen as an automotive fuel, we may be fixating on something that doesn’t have legs in the long-term,” he says. “Any day now the building equivalent of a Tesla could come along and change the game. Not long ago, who would have believed in the God particle? Now we know that it’s possible to solve problems on a molecular level. All the time and energy we’re putting into building technologies, including green roofs, can be made obsolete at any time. I suspect we’re on the cusp of bigger things.”

Assuming that’s true, should we back off green roofs? We may not discover another Higgs boson, but at least some of us are buried up to our wrists in dirt for a while. The larger problem isn’t water runoff or a lack of fresh produce — maybe it’s the disconnect from nature that seems to befall anyone who lives in the city for long.

“I don’t think it means we shouldn’t devote time and energy to what works for now — greener cities are healthier cities, no question,” he says. “I just think it means we might be surprised by what turns out to be a more permanent solution. The internal combustion engine survived virtually unchanged for a century. I think we’ve yet to hit on a green roofing technology that has that kind of staying power.”

Perhaps it doesn’t matter that those who write the bylaws and those who long for more nature in their concrete jungle have different motivations, as long as the end result works for both.

Feature image: Dundas Square Gardens by Easton's Group