Green roofs have been proposed as an efficient and practical tool to combat urbanisation in many countries. This review paper focuses on various benefits associated with green roofs and research efforts made till date to promote green roofs. Through systematic comparison of literature, this review also emphasises knowledge gap that prevail in green roof technology and highlight the need for local research to install green roofs in developing and under-developed countries. Considering that growth substrate, vegetation and drainage layer determine the success of green roof, efforts were made to consolidate desirable characteristics for each of these components and suggests methodology to construct practical green roofs. This critical review also explores limitations associated with green roofs and recommend strategies to overcome. Apart from stand-alone green roofs, there is a huge scope for hybrid green roof systems with other established techniques, which are presented and discussed. Recommendations for future study are also provided. (C) 2015 Elsevier Ltd. All rights reserved.