Evaluation of Green Roof System in comparison with Ordinary Roof from Energy Consumption Perspective of Energy Efficiency in line with Urban Planning (Mashhad Metropolis)1

Nowadays, the development of artificial surfaces in comparison with natural ones has become a fundamental challenge for the cities. Unstable development of the cities, which is resulted by the growth of technology and discharge of the balance between the environment and humans, needs to be changed. This research, aims at evaluating the function of green roof in comparison with casual roof in the city of Mashhad. In this regard, two simulation models one with green roof and the other without green roof are studied in similar conditions during summer and winter. The temperature of the roofs are measured and the thermal flux is also calculated by measuring the difference between the internal and external temperature. The results show that the fluctuation range of green roof is 70% less than the range of fluctuations in casual roofs in summer and 85% less in winter in Mashhad. As Mashhad is a cold city and needs heating systems most of the year, green roof can reduce energy consumptions in the buildings of the city. Green roof also reduces the cooling need in summer up to 11% and heating need in winter up to 19% by creating shadow and evaporative cooling in summer and minimizing thermal waste in winter. Therefore it can be concluded that green roofs are more than just beautiful and desirable spaces and they can increase energy efficiency of the buildings.