Issue link: http://digital.canadawide.com/i/178290
as well as state environmental of icials signed an agreement committing the city to a 'green infrastructure' network that includes green roofs, porous pavement, roadside plantings and more park space – all to stop rain where it falls, and allow it to ilter back into the ground, instead of into the stormwater system. "In the U.S., looding is an issue when it rains. What to do? Keep water away from the sewers," says Riaz Hasan, accessories product manager for Firestone Building Products. Last fall, its city hall water experts had a chance to learn even more about some of these measures, as Philadelphia hosted CitiesAlive 2011, a conference devoted to green roof technologies. Hasan, whose oversight encompasses North America and Europe, says the company's Skyscape system for green roofs is applicable to both extensive and intensive green roofs. "We use a German standard for the constituents of the growing media. They have a special blend of materials and must meet standards for water retention, iltration and mineral content and weight," says Hasan. Cities are taking increasingly urgent measures to curb in lows to their stormwater systems. Some in the U.S. Photos this page: Nathan Phillips Square, Toronto, ON. The transformation of the roof of Toronto's City Hall resulted in a 118,403-square-foot green roof are imposing ines on malls or other system. 2011 Green Roofs for Healthy Cities' Awards of Excellence winner in the Green Roof – Extensive Institutional category. Award recipient: PLANT building complexes for exceeding lim- Architect Inc. and Perkins + Will Canada (Landscape Architect/Architect). its. Cutting electrical consumption is also a growing concern. By proliferatFortunately, most Canadian cities have things customers like is simplicity. It's ing green roofs to address heat island effects, a city like Los Angeles could save billions in utility bills by reducing ambient summer temperatures by one degree climates that can quite easily accommo- one of our big drawing cards. But not just date green roofs. The exception is Calgary, simplicity, also the reliability of our prodFahrenheit, Hasan says. As climate scientists predicted, global warming is causing a higher incidence of says McGlade, because of the chinooks uct," says Kees Govers, technical sales extreme weather events, which, in turn, are forcing cities to act. "Weather extremes, that heat up the city for several days in representative for Liveroof Ontario Inc. drier, hotter, wetter or windier are more frequent, and the mid-temperate zone is mid-winter to plus ive or 10 degrees CelAdvantages include the opportunity moving north. The green roof is going to have an increasing role in dealing with sius, before the temperature drops sud- for a client to see the actual plants before excess water," says Terry McGlade, green roof specialist in business development denly to perhaps minus 18. installation, and have live plants growResearch indicates that green roofs' ing right away, without waiting a year or for Flynn Canada Ltd. For example, in 2008, the City of Toronto's stormwater system had to deal with ability to cut stormwater run-off is more for them to bloom. The focus, says the biggest water overload ever, says McGlade. Since 2000, Philadelphia has been hit impressive. The National Research Coun- Kees, is horticulture, not stormwater by a tropical storm or hurricane every two or three years. Between 1951 and 2000, cil's Institute for Research in Construc- management. tion (NRC-IRC) monitored a building in the city's average for such events was once every ive or six years. But, regardless which green roof sysToronto and found that a green roof cut tem a client buys, issues of extra cost and monthly stormwater run-off by an aver- warranty are often an obstacle, says John age of 47 per cent per month over a year. Mills, national technical manager at Sika Two green roofs types were used, one Sarna il Inc. "Often, it's a matter of changwith a growing media depth of 75 mil- ing the mindset. People that go for a green limetres and the other a 100 millimetre. roof tend to take the long view," he says. An electronic grounding screen Increased soil depth resulted in slightly installed below the membrane can pingreater water retention. Firms are using a range of systems. point the location of a leak, but does add Those from Xero Flor, which uses a to the cost, he says. Another way to address the warmineral wool for growing media, aim at combining convenience of installation ranty conundrum with respect to leaks with water retention, says Joy Schmidt, is instanced by the approach of the Roofpresident of Xero Flor Canada Ltd. "With ing Contractors Association of B.C. "Assoa whole system including the pre-grown ciation members' green roofs can be vegetation mat on top of the mineral wool, supported by the association's warranty, water retention is 50 litres per square which is ive to 10 years for waterproofing. The warranty program involves metre," she says. A modular approach that involves inspections to meet rigorous standards," initially growing the plants off-site and says Ivan van Spronsen, executive VP for installing them in trays is becoming pop- the association. ■ ular in part of convenience. "One of the Green Roof Systems p.34-39Greenroofs.indd 39 APRIL 2012 /39 3/26/12 2:23:02 PM