Reduction of energy consumption in residential buildings with green roofs in three different climates of Iran

In the current study, the modelling and simulation of energy consumption for a two-story building with green roof in three different climates of Iran (Bandar Abbas: hot and humid, Tehran: mild and dry, and Tabriz: dry and cold) have been performed. A typical building with asphalt roof and a complete identical building with vegetation on its roof instead of asphalt, on its last layer, has been simulated. Heat pumps have been used to provide heating and cooling loads on the building. The results of the simulation indicated that by the use of green roof, the annual baseline electricity consumption for heating and cooling loads was reduced up to 16.3%, 12.5% and 23% in Tehran, Tabriz and Bandar Abbas, respectively. Use of green roofs in the tropical regions (Bandar Abbas) is more efficient compared to cold regions (Tabriz). The reason behind this phenomenon is the effect of the green roof as a cooler on the performance of the studied building's cooling system. Payback time for the initial construction of green roofs, due to energy savings, is 11, 10 and more than 40 years for Tehran and Bandar Abbas, respectively.