Plant and turf providers are expected to benefit as Toronto’s city council passes a new bylaw setting minimum “green roof” requirements on all classes of new buildings.
The city bylaw, passed Tuesday, will require up to 50 per cent green roof coverage on multi-unit residential dwellings over six storeys, schools, non-profit housing, commercial and industrial buildings. Larger residential projects will need greater green roof coverage, ranging anywhere from 20 to 50 per cent of the roof area.
“This bylaw is a major part of the solution to climate change, the creation of green jobs and it represents a whole new mindset on how our cities approach the 20 per cent or so of surface area that are roofs,” Deputy Mayor Joe Pantalone said in a release Wednesday from Green Roofs for Healthy Cities, (GRHC), the North American green roof industry association.
“The bylaw breaks new ground on how to structure a mandatory green roof requirement and the construction standard also contains important best practices that may prove to be a model for other cities,” GRHC president Steven Peck said in the same release.
The mandatory bylaw in Toronto is expected to result in about 50 to 75 new green roof projects annually.
The city already requires green roofs on city-owned properties, offers a financial incentive of up to $5 per square foot for existing buildings, and is now building a “publicly accessible” green roof on its city hall.
A study done for city council by Ryerson University in 2005 outlined a number of benefits from a “green roof” policy, including reduced flow of stormwater (and reduced sewer backup in areas of the city served by “combined” stormwater and sewage systems), improved air quality, reduced direct energy use, and reduced “urban heat island” effect.
Based on those benefits the study pegged the initial cost savings in the city at about $313.1 million and annual cost savings of $37.13 million, assuming full use of the area available for green roofs across the city at about 5,000 hectares.
Among the minimum requirements Ryerson considered were that the roof system be of the “extensive” type, that it cover a “significant” portion of the roof, have a maximum runoff coefficient of 50 per cent, and have a minimum depth of 150 millimetres (about six inches) where structural loads allow.
The Ryerson report also pointed to other benefits that “could not be quantified in this report” such as aesthetic improvements to the urban landscape, increased property values, potential use for food production and increased biodiversity.