Environmental Management
Heavy Lifting Leads to Transformed Space Green Roof Retrofit Poses Some Challenges
Photos courtesy of Gardens in the Sky
By Terry McGlade
ESRI Canada, a leading geographic information systems (GIS) software company based in Toronto, recently revamped its headquarters in a heavily trafficked older industrial area adjoining the Don Valley Parkway with a green roof. Company President, Alex Miller, envisioned the project as way to promote environmental responsibility and also cheer up the somewhat austere surroundings. “We wanted to create a demonstration of an environmental asset for the city on our roof,” he says. “Opaque surfaces in the sun can easily reach 40, 50 and even 60° C, but vegetation brings in temperature control because leaves are about 21° C all the time. If 8% of all existing roofs in Toronto were green, surface temperatures in the city would be reduced by one to two degrees Celsius.” Planning began in 2007 with input from the building’s landlord, Crown Property Management. The project faced several challenges, including winds, load capacity, building height and the need to protect and avoid damaging the glass curtain wall. Because the green installation was going on an existing 20-year-old roof that hadn’t been built to accommodate it, some structural reinforcement was required. The designer opted for a modular system for the 7,100-square-foot (660-square-metre) surface, which allows for sections to be removed and
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re-installed whenever repairs are required to the building. Wind velocity, particularly at six storeys above ground, was factored into choosing and installing the plants. An 85-ton crane was employed for the heavy lifting, which included eight-foot pine trees each planted in a 36-inch root ball and a separate container. The total project encompassed 100 yards of soil, 56 planter boxes – 14 of which measured four feet in height, width and length – and 4,000 individual modules of live root plants, which, at 65 pounds each, collectively weighed 260,000 pounds. Further complicating the schedule, crane availability and other logistical considerations in a building housing day-to-day business meant that work could occur only Saturdays and Sundays. This was carried out with a crew of eight working
20 november 2009 PROPERTY MANAGEMENT REPORT
12-hour days for three weekends in early May 2009. Luckily, there were no high winds until after the craning work was complete. Capital costs for the ESRI installation are in the range of $25 to $35 per square foot. However, it qualified for a grant from the City of Toronto’s 2009 Eco-Roof Incentive Program for Green Roofs in Toronto, which provides an incentive of $50 per square metre ($4.60 per square foot). On the operating cost side of the equation, other benefits can be seen as green roofs: • retain rainwater, which reduces runoff and minimizes storm drain requirements • cool surrounding air and reduce ambient heat • absorb airborne toxins and provide additional land area • provide better heat and sound insulation • improve air quality