Reduction in residential energy consumption via modifying the details of green roof architecture in a warm and semi-arid climate, Dezful, Iran

In the subject of climate and architecture, the most impressive element of building against climate factors is the roof of building. The energy received by the roofs in summer is much more than other building walls which leads to increase the energy consumption of the cooling system in the space under the roof. On the other, the major of energy consumption in cooling, electric energy is considered as more expensive energy that will have a large share in household consumption costs. In winter, the heat loss of the roof from inside to outside leads to an increased in energy consumption of the heating system. It affects the residential energy consumption significantly. One applicable recommendation for decreasing heat transfer is to use green roofs. In green roofs due to vegetation, soil and various layers, the heat is converted to moisture through evaporation, and generated cooling leads to cooling of buildings. In other words, green roofs help reduce heat fluctuations, shade and increase heat capacity to cool the space under the roof in the summer and winter heating On the other hand, all effective parameters on the thermal performance of green roofs must comply the climate conditions of the region.

these two questions arise: What are the effects of green roof layers on optimizing the thermal performance and energy consumption of residential building as well as thermal comfort of the people living in the climate of Dezful city? And what are the best details of the green roof in terms of reducing domestic energy consumption in the geographical location of Dezful? Research Aimes: This study is aimed at investigating the effective parameters of green roofs on improvement of their thermal performance as well as proposing a suitable green roof design for of Dezful city, Iran.Research

For this purpose in initial studies and by proving the needs, the present study is based to complete the basic knowledge about various aspects of green roofs and the principals of their design and implementation via a qualitative study and comprehensive investigation of literatures. followed by investigating the influence of various indexes and effective parameters on thermal performance of green roofs for residential building is modeled in the climate conditions of Dezful via an experimental research method and transferring the data obtained from resources, statistics given by the weather station of Dezful as well as “Dview” and “Climate Consultant” software to the simulating software of “Design Builder”.All results were compared with an ordinary roof and Finally, the most optimum situation for the layers composing the green roof of this region was determined.

Measurements have revealed that the thermal performance of green roofs in the climate conditions of Dezful is affected by herbal species containing wide leaves with high cover have the greatest impact on reducing the cooling and heating load of the building and reducing its costs. After than, low growth and low depth of growing media can also reduce the cost of cooling and heating. The effect of the green roof with air layer, insulation layer and use of rubber crumbs as drainage layer is lower than the previous three factors, but its use is valuable. In general, the modification of green roof layers has resulted in 8.42 kWh/m2 energy reduction which is equal to 29.2% of the total energy consumption of the simulated building and consequently results in an annual saving of 1291.037 $ from the energy consumption costs.