This study investigated the effect of green roofing on energy and fuel saving and the consequent reduction in pollutant emissions in Mashhad in the hot period of the year. The DesignBuilder software package was used to model and simulate a sedum-vegetated green roof with 10-cm-thick dry soil on a 350-square meter building. The reduction in cooling load (energy saved during the hot period of the year) due to this green roof was estimated to 7.9 kWh/m2 year. The rest of the estimations were performed based on three scenarios where the roof area available for the implementation of green roof projects in the city was assumed to be 7.8, 45, and 96 million square meters, respectively. In these scenarios, the total energy saving in the hot period of the year was estimated to 61,620, 355,500, and 758,400 MWh, respectively. It was also found that the reduced consumption of fuel in power plants because of the reduced demand for energy would result in 0.7–9 million dollars’ worth of cost-saving every year. The results of the scenario analysis showed that the emission reductions due to the implementation of green roofs would be in the range of 17.5 and 299.3 (ton/year) for PM10, 17.3 and 215.8 (ton/year) for CO, 154.9 and 1905.9 (ton/year) for NOx, and 280 and 3445.9 (ton/year) for SO2. The total reduction in the environmental damage costs of pollutant emissions in the three scenarios was estimated to 2.45, 14.21 and 30.32 million dollars per year, respectively.

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