Employing thermal insulation in buildings’ exterior walls is an effective technical measure to reduce energy consumption and carbon emissions of buildings. A multi-objective optimization method is presented for exterior wall insulation in buildings based on the equivalent full-load hours-based energy consumption (EFLHEC) prediction method, comprehensive analysis(economic, energy, and carbon emission) models, and assessment indexes. The presented optimization design method consists of an EFLHEC-based energy consumption prediction module, a comprehensive analysis model-based quantitative evaluation module, and a balanced index-based optimal design scheme determination module. Comprehensive analysis models are developed to evaluate economic performance, energy, and carbon emissions of external wall insulation. The balanced index method is extended to cope with economic, energy, and carbon emission factors of buildings’ external wall insulation. The research results showed that the EFLHEC provided an accurate and simple energy consumption prediction method for buildings’ exterior walls. The optimal design scheme was determined by comparing the values of balanced indexes for different design schemes of external wall insulation. Cooling and heating source type had important influences on the optimal insulation layer thicknesses, economic performance, and carbon emissions of external wall insulation in buildings. The largest variations in the balanced index for different types of insulation and different types of cooling and heating sources were 0.14 and 0.41, respectively. The cooling and heating source type should be considered in optimizing the design of external wall insulation in buildings. The best solution was obtained by EPS and natural gas for an office building in Zhengzhou city in China. The presented multi-objective optimization method is very helpful in solving the complex engineering problem of optimizing external wall insulation.

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.

The use of thermal insulation material in building envelopes is closely related to economic benefits, energy-savings, and carbon reduction of buildings. The construction forms of different components in building envelopes have an important influence on the optimization design of thermal insulation in building envelopes. In this study, an integrated optimization approach is proposed to search for the best solution of thermal insulation in external walls and the optimal combination scheme of different construction forms of envelope components in granaries. The integrated optimization approach consists of an orthogonal experimental design (OEDM) method-based determination module of an optimal combination scheme of different construction forms of components, an assessment model-based quantitative analysis module, and an integrated assessment indicator-based selection module of the best solution of external wall insulation. Firstly, the OEDM method is used to determine the optimal combination scheme of different construction forms of the foundation wall of an external wall, thermal insulation material, external window, roof, and floors in buildings. Secondly, integrated economic, energy, and carbon analysis models are developed to analyze comprehensive performance of external wall insulation. Finally, an integrated assessment indicator consisting of an energy balanced index, a carbon balanced index, and weight coefficients is presented to determine the best solution of external wall insulation. The applications of this optimization approach in different ecological grain storage zones in China demonstrated that the outdoor air temperature characteristics could affect the comprehensive performance of external wall insulation in granaries, significantly. The best solution of external wall insulation in granaries in Turpan city, Daqing city, Kaifeng city, Changsha city, Anshun city, and Danzhou city was expanded polystyrene insulation (EPS) with a layer thickness of 0.078 m, 0.048 m, 0.083 m, 0.089 m, 0.062 m, and 0.131 m, respectively. The greatest difference in the lowest entire construction cost and the lowest carbon emission of external wall insulation among different typical climate regions in China was 12.987 USD/m² and 6.3 kgCO2e/m², respectively.