Toronto is the first major city in North America to institute a bylaw requiring all new development to have a green roof. The law took effect in 2010, and requires new buildings with floor space over 2,000 square meters to devote 20 to 60 percent of its roof to vegetation. The law applies to residential, commercial, institutional, and industrial buildings.

Not all Toronto developers were happy with the green roof mandate. In 2009, Stephen Upton, vice president for development at Tridel Corp, a Toronto high-rise condominium developer, said in a Reuters report: "I don't think anybody is warm and fuzzy about having a green roof bylaw impressed on them as a prescriptive method.”

Toronto encourages healthier roofs for existing buildings via Toronto’s Eco-Roof Incentive Program which provides grants to promote green and cool roof retrofits on Toronto’s existing industrial, commercial, and institutional buildings. The incentives provide a per square meter subsidy for a green roof up to 50 percent of the cost (maximum of $100,000), and a per square meter subsidy for a cool roof, up to 50 percent of the cost (maximum of $50,000).

The Toronto Environment Office explains the benefits of green and cool roofs: “Green Roofs help reduce operational costs to Toronto Water to treat storm water that is retained by the eco-roof. Green and cool roofs also help reduce the Urban Heat Island effect that occurs during summer heat waves as green roofs help to cool the local air as a result of the cooling effect that takes place when water is evaporated. Cool roofs reflect sunlight back into the atmosphere and negate its warming effect resulting in reduced demand for air conditioning. "

New York City is also actively encouraging green and cool roofs for the city. While not having a mandate or bylaw, New York has several initiatives to encourage green and cool roofs. The NYC Green Roof Tax Abatement allows a tax abatement equal to $4.50 per square foot of green roof space. The maximum benefit of the abatement is $100,000 or the tax liability of the eligible building – whichever is less. Condominium abatements are apportioned to the individual condominium units.

NYC also has the NYC °CoolRoofs program, an initiative that seeks to reduce carbon emissions, cut energy use and lower temperatures by helping property owners apply a white, reflective coating to their rooftops. During the program’s inaugural season last year, more than one million square feet of rooftop was coated throughout the five boroughs, with nearly 2,000 New Yorkers volunteering to help coat rooftops.

According to Toronto-based Green Roofs for Healthy Cities, New York City ranks third in the USA for amount of green roofs installed per square footage, following Chicago and Washington, DC. When looking at all of North America the leaders in amount of green roofs are Chicago, Toronto, and Washington. DC, in that order.

With or without government mandates, it's smart for NYC, along with Toronto and other cities across the world, to keep promoting healthier roofs. In 2010 PlanNYC announced a campaign to install green roofs, porous sidewalks, and parking lots, in order to capture excess rainwater and runoff that causes major pollution to flow into New York's waterways.

PlaNYC has a goal of making 90 percent of New York City’s waterways suitable for recreation: a worthy goal since New York's extensive waterfront is so polluted that the majority of it is not suitable for swimming and recreation. PlaNYC's strategy to vastly increase the amount of green surfaces would eliminate 40 percent of the existing runoff into the waterways and save taxpayers $2.4 billion in storm water and sewage costs over the next 20 years.

Watch out Toronto, Chicago, and Washington, DC, because NYC might just have more urban green than you do in the near future.

Paul McGinniss is the Green Advocate for New York House magazine. Check out his blog The New York Green Advocate. You can email him at greenadvocate@scheimedia.com