The place of green roof system in mitigation of urban heat island case study:karaj

Based on the statistical evidence، The Earth''s climate is warming and it happened particularly in the urban areas. For example، the annual average temperature in Iran''s third largest pollution metropolitan-Karaj، during the period 1960 to 2008 increased about 2. 256 degrees Celsius. The heating effect on the human environment has more features and derived urban heat island becomes more severe and lead to increasing air pollution in urban environments. Energy consumption increased to create favorable conditions of human living. Generally increasing temperature in urban environments poses serious problems and costs. The only way to prevent or at least mitigate these problems is Change the physical structure of the city in order to adapt the heating suitable place. Due to the high value and low land area of green space in the metropolitan cities،it seems that choosing green roof technology in large cities is a suitable altenative because of improved quality and it،s impact on sustainability of the urban environment. The main objective of this research is to introduce green roofs system and its impact on reducing the heat-island phenomenon. The temperature effect of green roofs in comperative study with other roofs were analyzed on micro climate scale and simulated by using Derob software. The finding is clearly shown that there is considerable reduction in temperature capacity. The results show that impact of heat island can be reduced by developing green roofs in the future constructed buildings in comparison with other roofs.