Comparative Comparison of the Effect of Green Roof Vegetation on the Reduction of Urban Heat Island (Case Study: Enghelab Square, City of Tehran)

The compact development of cities and the reduction of green spaces are the main reasons for the formation of thermal islands, a phenomenon that has become a major problem in cities. In addition, increased temperatures have led to environmental problems, reduced health of citizens, and risen energy consumption, particularly in buildings as it is used to create favorable temperature conditions to gain thermal comfort. One strategy for controlling and reducing this problem is the use of passive systems such as green roofs which can affect the thermal properties of a building due to their moisture content, absorption level, reflection and shading parameters. Furthermore, the presence of different vegetation will have different effects on the temperature changes of the roof surfaces. This paper investigates the performance of green roofs with different vegetation coverage on the roof surface temperatures of buildings. The surveys were conducted in hot and dry climates of Tehran city and simulations were carried out by Envi-Met software. The main environmental variables such as mean radiant temperature, air temperature, air flow and relative humidity were studied and compared as the main variables of the study. Finally, a comparison of the extent and role of the above on reducing the thermal island phenomenon shows that the use of Hedege, Grass and Soja vegetation in creating optimal conditions was very impressive in the order mentioned. The results show that green roof with Hedege vegetation (compact) had the greatest impact on climatic parameters compared to other green roofs.