Green roof benefits include: urban heat-island reduction, mitigating air pollution, reducing rainwater runoff and increasing urban biodiversity. In addition green roofs have aesthetic benefits, and can be an excellent medium for urban agriculture. This paper suggests a method to evaluate the potential for green roof retrofit on a large urban fabric. GIS based analysis methodology was established and applied to the city of Netanya, Israel. Based on the analysis 0.85 km2 (1,214 buildings, 9 % of total buildings) was found to be suitable for an intensive green roof system, and 0.92 km2 (3,004 buildings, 22 % of total buildings) was found to be suitable for an extensive green roof system.