Study on Building Energy Consumption and Control (I) ——Wall’s Transmission Load and Thermal Performance under Natural Ventilation

This study deals with thermal performance of south-facing walls (uninsulated, external insulated and internal insulated) under the condition of natural ventilation. Expanded polystyrene(EPS) as insulation material is selected. The yearly cooling, heating and total transmission loads are calculated by using an unsteady heat transfer numerical model under the climatic conditions of Chengdu, China. Results show that the employ of thermal insulation is advantageous in decreasing yearly heating load while unconspicuous in decreasing yearly cooling load. The trend of yearly cooling load changing with insulation thickness of external insulation is entirely different from that of internal insulation. However, the variation of total load with the thickness of external insulation is the same as that of internal insulation. By comparing the two curves, it is obvious that internal insulation is more advantageous than external insulation for south-facing wall in Chengdu. In addition, Improved Genetic Algorithm(IGA) is proposed to determine the optimal thickness of external insulation for yearly cooling load and to help the designer selecting the correct insulation method(external insulation or internal insulation). The results show that when the optimal thickness of external insulation is 44mm, the yearly cooling load is minimum. In order to achieve the goal of 65% energy saving, 39mm and 62mm are adopted for internal insulation and external insulation, respectively. The IGA proposed in this study can be used to solve the similar inverse problems in energy saving effectively.