October 29, 2012
RECOVER GREEN ROOFS
The nuts and bolts of urban agriculture and green roofs
As Toronto intensifies thanks to the condo boom and provincial government policy preventing suburban sprawl, it seems absurd to picture lettuce fields and chickens downtown.
But, with a growing number of developers installing green roofs for environmental, economic and aesthetic reasons, and city dwellers largely reliant on food trucked from afar, farming in the city is closer than you might think.
Green Roofs for Healthy Cities and FoodShare Toronto organized a conference, the Urban Agriculture Summit, at Ryerson University this summer to share ideas and discuss projects already underway across North America and beyond.
Debbie Field, executive director of FoodShare Toronto, said food production in cities isn’t entirely new given the victory gardens of the Second World War. FoodShare launched in 1985 after then-Toronto mayor Art Eggleton responded to demand from people in low-income neighbourhoods who wanted to develop community gardens.
“Twenty-seven years later the movement has gone from community gardens mostly in social housing and on public land through to beginning to think about the built form and load-bearing issues,” Field said.
Martin Blake, vice-president of Daniels Corp., said the developer has promoted the food growing capabilities of its balcony spaces and rooftop gardens but hasn’t found this an easy selling point.
“People tell us it’s great but do they get granite countertops,” Blake said.
“We have to change their thinking.”
Sheila Penny, chief architect with the Toronto Lands Corporation, said a couple of Toronto public schools, including Bendale Business and Technical Institute, have incorporated rooftop food gardens into multiple aspects of the curriculum.
With acres of available land at more than 500 school properties, “it’s a no-brainer...to transform oceans of asphalt into richer, more diverse environments,” Penny said.
Toronto architect Monica Kuhn said there are many advantages to local urban food production, including job creation, local self-reliance, savings realized by reducing or eliminating transportation, and maximum freshness.
“It doesn’t have to be on a truck all week. It was on the roof and it’s ready for lunch.”
Kuhn, accredited through Green Roofs for Healthy Cities as a green roof professional, said rooftops often house mechanical equipment but are otherwise underused, and gardens encourage stormwater retention and filtering, reduce combined sewer overflows, and lower smog and the summertime heat-island effect.
However, Kuhn said design considerations come into play when planning rooftop gardens, whether on new or existing buildings.
A structure’s load-bearing capacity is vital because fully-saturated soil is heavy.
“Wet soil weighs 100 lbs. a cubic foot, and most roofs are designed for 40...so you have to figure out what the building is designed for and what it can hold.”
Roof membranes have a limited life-span and need to be sound. “You don’t want to be blamed for a leak that was already happening,” Kuhn said.
Developers and builders need to get materials, including soil, safely to the rooftop. Methods can include a crane, hoist or blower truck, but these must be able to reach the building.
“It’s a design project. As with a park or a building, a garden has design parameters you have to think about,” Kuhn said, adding that zoning, permits and other approvals can also come into play.
Kuhn pointed to some early, creative examples, including an abandoned overpass in Montreal and a Boston-area restaurant, The Ledge.
“The menu changes daily depending on what’s coming off the roof.”
The conference also set the stage for the official release of GrowTO, a 24-page self-described “urban agriculture action plan” for growing food in and around Toronto.
GrowTO outlines accomplishments to date, including community gardens in public spaces, greenhouses attached to seniors’ residences, and the City’s Green Roof Bylaw.
The document also acknowledges beekeeping and aquaculture projects for honey and fish, but highlights a major sore point for many urban agriculture supporters — the City’s current ban on backyard egg-laying hens.
Recommendations include identifying structurally-sound rooftops across the city, creating an urban agriculture zoning category, updating Toronto’s official plan to more strongly endorse agriculture and community gardens, and recognizing urban agriculture as green infrastructure — for instance, as part of stormwater management plans.
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