Canadian Consulting Engineer


Roofs and the Environment

Test roof garden at the National Research Council Field Roofing Facility in Ottawa. Researchers monitored two roof sections, one a vegetative roof, and the other a conventional modified bituminous roof, over a two-year period. The green roof's thermal mass was found to dramatically reduce surface temperature fluctuations and reduce the building's cooling load by 75%. The 150-mm (6") roof planting system also retained up to 8 mm of rain water and reduced run-off by 75%. Another test site with vegetation on the walls reduced the cooling load even more. The report calculates that assuming even a small market penetration, over 10 million square metres of green roof could be constructed in the city of Toronto by the year 2010. "Evaluating Rooftop and Vertical Gardens as an Adaptation Strategy for Urban Areas," NRCC-46737, final report by Brad Bass and Bas Baskaran, Sept. 2003.