Determination of optimum insulation thickness based on cooling transmission load for building walls in a hot climate

► Thermal and economic parameters for insulated walls in a hot climate are investigated numerically. ► The investigation is carried out for different wall orientations during the summer period. ► Cooling load, time lag and decrement factor are calculated under steady periodic conditions. ► The insulation thickness is optimized according to cooling requirements of buildings. ► Results are compared with the degree-days and degree-hours methods. The main objective of this study is to determine optimum insulation thickness according to cooling requirements of buildings in a hot climate. The investigation is carried out using an implicit finite difference method under steady periodic conditions for different wall orientations during the summer period in Antalya, Turkey. For this purpose, a computer program developed in Matlab is utilized. Firstly, thermal characteristics such as cooling transmission load, time lag, and decrement factor are calculated. Then, the optimum insulation thicknesses for all wall orientations are determined by using a cost analysis over lifetime of 20years of the building. It is seen that for cooling season, the lowest value of optimum insulation thickness is obtained for the north-facing wall which has minimum cooling load while the highest thickness is obtained for the east and west walls providing the maximum cooling load. The results show that for cooling season, the most economical orientation is north with an optimum insulation thickness of 3.1cm. Results obtained are also compared with the degree-days and degree-hours methods.