The fight for Montreal’s environmental future has recently reached new heights, as various environmental groups in the city promote the installation of energy-efficient green and white roofs.
Green rooftops, or rooftop gardens, are becoming more and more popular in Montreal, while white rooftops, flat surfaces with a white polymeric membrane stretched across, are just starting to be introduced.
In spite of the trend, though, Tim Murphy, green projects coordinator for Santropol Roulant, said that the City could be doing a lot more to promote sustainable design.
“Montrealers are behind in rooftop gardening,” he said.
Murphy did, however, note the presence of community and collective gardens around Montreal, including a community garden in Milton-Parc, as evidence of their growing popularity. There are also rooftop gardens on the Maison de la culture and the library in Côte-des-Neiges, the Quebec RCMP Headquarters in St. Henri, and the McGill Life Sciences Complex.
The environmental benefits of such rooftops are hard to ignore.
“Green roofs reduce the amount of energy needed to cool down a building,” said Patrice Godin, the project manager for the Urban Ecology Centre’s (UEC) “Cool Island” Greening Project.
Murphy, who worked with McGill’s School of Architecture to develop the green space outside Burnside Hall this fall, also commended the efficiency of green roofs.
“They prevent storm water runoff and improve water filtration,” he said. “It also has psychological benefits. It’s soothing and relaxing, and it can help people escape.”
These rooftop gardens are a pricey escape, however: a green roof costs from 10 to 15 dollars more per square foot than a normal roof.
“The green roof is not without issues,” said Dennis Fortune, director of McGill’s Office of Sustainability. “You have to include maintenance in the operations. After a while, someone will have to maintain it.”
That person would be Eric Champagne, the horticultural supervisor for buildings, grounds, and special events in university services, and his staff.
“We have to pull the weeds out before they get too big, and the seeds are so lightweight, they fly on top of tall buildings and grow fast,” said Champagne. “This is on top of everything else we’re doing. We have all the grounds to take care of.”
Champagne did acknowledge that the first year of managing a rooftop garden is the hardest, and that maintenance responsibilities should decrease annually.
“We used [perennial] plants that don’t require much care, [and] once all the weeds are weeded out, it will be easier to maintain,” Champagne said.
The economic burden and time commitment of rooftop gardens has Fortune looking to white roofs as a cheaper, comparatively effective alternative. White rooftops can be constructed using white gravel, or by painting the rooftop with a special white primer.
By increasing the reflectivity of a roof, preventing excess heat from being trapped inside the building, they can lower the heat of urban centres and reduce a building’s use of air conditioning. And by contrast to the steep price of a green roof, a white roof is only likely to cost two to three dollars more per square foot.
“It changes the microclimate of large buildings,” said Fortune. “They also make indoor occupants more comfortable. [They can help] people with breathing problems.”
McGill and the Office of Sustainability have already started testing white roofs on campus, installing white membranes on the roofs of the student residence at 3471 Peel and the Strathcona Music Building. A McGill report on the effect of the membrane showed that it could lower the heat of the building by 15 degrees Celsius. White roofs, however, also have their shortcomings, especially in comparison to rooftop gardens.
“Green roofs are more effective in terms of cooling down [a building] than white roofs, [but] they don’t have the same benefits in terms of water management,” said Godin.
At the centre of the roof question is the “heat island effect” – the occurance of warmer temperatures in urban landscapes compared to rural areas resulting from the retention of solar energy on constructed surfaces.
Last year, former McGill Engineering student Philip Sawoszczuk presented a report to the Office of Sustainability describing the heat island effect for McGill’s downtown and Macdonald campuses. The report showed that urban construction and waste heat could raise temperatures by almost six degrees Celsius in downtown Montreal. The report identified flat-roof membranes like the one on 3471 Peel as a means of reducing the temperature build-up on campus.
“We have to look at what’s best for this place,” said Fortune. “We’re looking at reducing the heat island effect on roofs and hard surfaces [like terraces]” at McGill.
Montreal’s municipal government doesn’t seem to be climbing on the rooftop ecology bandwagon, however, and local environmental groups like the UEC and Santropol Roulant are struggling to promote the new energy efficient solutions without government legislation and economic incentives.
“The City hasn’t done a whole lot to promote green and white roofs in terms of policies and economic incentives,” said Godin.
Godin cited legislation passed in Toronto as an example of how far behind Montreal is. According to Godin, newly constructed buildings in Toronto with more than 1,000 square metres of roof space have to set up a green roof on at least half the area. He also said that Toronto has created an economic incentive for developers to build green roofs, with the municipal government subsidizing five dollars per square foot for people who develop green roofs on their properties. Godin added that this however, is just one small contribution to creating an environmentally sustainable city.
“The green roof is one part of the global strategy to fight urban imbalance,” said Godin.