Monitoring of side-by-side roof systems in Toronto, Canada, measured a conventional black roof membrane at 66°C (151°F) on a typical summer day, while green roof membrane temperatures peaked at 36-38°C (97-100°F). The green roof reduced the average daily heat flow through the roofing system by 70-90% in the summer and 10-30% in the winter.
Liu, Karen K.Y., and Bas Baskaran. (2005). Thermal performance of extensive green roofs in cold climates. National Research Council Canada: Institute for Research in Construction, NRCC-4820.