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Stormwater management solutions are needed to increase resiliency within urban areas by: (1) maintaining the natural hydrologic cycle, (2) controlling erosion and flooding, and (3) protecting water quality (MOE, 2003). Large impervious areas from urban development results in the loss of vegetated surfaces which leads to an increase in direct runoff (e.g. Paul and Meyer, 2008). Within urban areas, conventional roofs cover 40-50% of the impervious surfaces giving them significant potential to host urban stormwater management solutions (Dunnett and Kingsbury, 2004). Green roofs are able to restore the altered hydrologic cycle closer to its natural state by reducing the volume of runoff from a roof as well as attenuating flowrates. The hydrologic benefits of green roofs are partially attributed due to the vegetated surfaces enhancing evapotranspiration (ET) in urban areas. Predicting ET from green roofs is critical to inform green roof design and for optimization of hydrologic performance. This study focuses on evaluating the influence of green roof design parameters, such as vegetation type and growth media depth, on ET and by extension the hydrologic performance of an extensive green roof. While many studies have now demonstrated the effectiveness of green roofs in attenuating flowrate and reducing the volume of stormwater runoff (e.g., VanWoert et al., 2005a, Fassman-Beck et al., 2013, Berndtsson, 2010), little field research has been completed on directly quantifying ET rates and the hydrologic benefits green roofs in Canada including the influence of different vegetation types. The lack of available data on ET rates from green roofs limits optimal green roof design under the Canadian climate.