Effect of cool and green roofs on the thermal comfort, energy savings and carbon emissions under dry desert climate

With the growth of cities, roads and buildings have gradually replaced the vegetation of the region, which has caused a significant increase in air temperature of urban areas compared to rural regions. This phenomenon affected the thermal comfort of the indoor and outdoor environment, final energy consumption and the health of society. Considering that the roofs of buildings consist a large part of urban surfaces, it is evident that using suitable roof techniques can improve both the environmental conditions of cities and building s thermal performance. In this article, the impact of cool and green roofs on the thermal comfort, energy saving and carbon emission is investigated for a dry desert climate. For this purpose, the thermal performance of a common residential building with two types of insulated and non-insulated designs was simulated in EnergyPlus. Three types of cool roofs with albedos of 0.5, 0.7 and 0.9 and two types of green roofs, one naturally exposed to atmospheric precipitation and the other always kept moist, were considered. The results indicated that roof coating can reduce the average and maximum operative temperature on the hottest day of the year by 14.2 and 12.9%, respectively. It was shown that while wet green roof provides savings in energy consumption and environmental emission, dry green roof has not a positive environmental impact under the dry desert climate. Overall, the optimal roof techniques reduced the annual thermal loads and carbon emissions by 19.6-34.5% and 45.3-56.5%, respectively.