The design of thermal insulation in roofs is very important to reduce energy consumption and decrease the environmental impacts of buildings. An integrated economic and environmental assessment-based optimization design method is presented in this paper to find the best candidate insulation design scheme for building roofs, including the determination of roof thermal insulation type and the optimum insulation thickness. In the optimization design method, a zonal method-based double-skin ventilation roof heat transfer model is developed to predict the roof energy consumption. Economic and environmental benefits due to thermal insulation are calculated by using the economic analysis model, the environmental analysis model, and roof energy consumption. Moreover, an integrated dimensionless economic and environmental assessment index is proposed to evaluate different roof thermal insulation design schemes. The optimum insulation thickness is determined by maximizing the sum of economic benefit and environmental benefit due to thermal insulation. The validation results in a real building show that the predicted data for the zonal-based double-skin ventilation roof heat transfer model agreed well with the measured data, with a maximum relative error of 8.2%. The optimum insulation thickness of extruded polystyrene (EPS), mineral wool (MW), and polyurethane (PU) was between 0.082 m and 0.171 m for the single-skin roof in a low-temperature granary in Changsha region in China. The ranking of the integrated assessment indexes of thermal insulation is EPS > MW > PU. A double-skin ventilation roof can reduce the optimum thickness of thermal insulation. The best result is obtained by EPS for the double-skin roof with a grey outer surface color for the low-temperature granary roof in Changsha region in China. The influencing factors of insulation type, roof structure, and roof outer-surface color should be considered in finding the best candidate insulation design solution for building roofs. The integrated economic and environmental assessment-based optimization design method can help designers to efficiently find the best design scheme of thermal insulation to maximize the sum of economic benefit and environmental benefit for building roofs.

The optimization design of buildings is very important to the energy consumption, carbon emissions, and sustainable development of buildings. The low-temperature granary has a low grain storage temperature and high energy consumption indexes. The design scheme of the roof insulation for a low-temperature granary should be determined in actual building design processes by considering the costs, carbon emissions, and outdoor climate, comprehensively. In this paper, a new low-carbon optimization design method is proposed for the roof insulation in the low-temperature granary. The low-carbon optimization design method can respond to the cost issue, emission reduction issue, and outdoor climate issue, simultaneously. Moreover, the low-temperature granary roof insulation of different ecological grain storage zones in China is optimized in terms of carbon reduction by using the proposed low-carbon optimization design method. The application results of the optimization design method in different ecological grain storage zones in China indicate that the outdoor climate has significant impacts on the economic performance and carbon reduction effect of roof insulation. The cost considerations related to carbon emissions can apparently increase the economic efficiency of roof insulation. The optimal economic thicknesses of expanded polystyrene (EPS) in the cities of Urumqi, Harbin, Zhengzhou, Changsha, Guiyang, and Haikou are 0.025 m, 0.037 m, 0.085 m, 0.097 m, 0.072 m, and 0.148 m, respectively. The different outdoor climates of the seven ecological grain storage areas in China have important influences on the comprehensive economic performances of low-temperature granary roof insulation. The design of the low-temperature granary roof insulation in Haikou city has the best economic performance among the seven ecological grain storage zones in China.

The optimization design of buildings is very important the energy consumption, carbon emissions ,and sustainable development of buildings. The low-temperature granary has low grain storage temperature and high energy consumption indexes. The design scheme of roof insulation for low-temperature granary should be determined in actual building design processes by considering economy, carbon emissions, and outdoor climate, comprehensively. In this paper, the low-temperature granary roof insulation for different ecological grain storage zones in China are optimized by using a new low-carbon optimization design method. The low-carbon optimization design method can response to the economical issue, emission reduction issue, and outdoor climate issue, simultaneously. The application results of the optimization design method in ecological grain storage zones in China indicate that outdoor climate has significant impacts on the economic performance and carbon reduction effect of roof insulation. The considering of carbon emission cost can apparently increase economic efficiency of roof insulation. The optimal economic thickness of expanded polystyrene (EPS) in Urumqi, Harbin, Zhengzhou, Changsha, Guiyang and Haikou cities is 0.025 m, 0.037 m, 0.085 m, 0.097 m, 0.072 m and 0.148 m, respectively. The different outdoor climates of seven ecological grain storage areas in China have important influences on the comprehensive economic performances of low-temperature granary roof insulation. The design of low-temperature granary roof insulation in Haikou city has the best economic performances among the seven ecological grain storage zones in China.