Optimization of thermal insulation thickness applied to building external walls considering economic parameters

In this study, the calculation of an optimum thermal insulation thickness, payback period of the insulation cost and insulation cost for the different insulation materials and different lifetime period, for Bursa, located in the second degree-day (DD) region in Turkey, was carried out in case of being zero of the rate of real interest and being different from zero of the rate of real interest. Both the heating and cooling DDs and the annual heating and cooling energy requirements were calculated by using the current outside air temperatures for Bursa. It was found that the heating energy requirement was 5.5 times greater than the cooling energy requirement for Bursa. When the economic parameters were considered (the real interest is % 5, the lifetime period is 10 years), the optimum insulation thickness was found as 3,8 cm for EPS, as 3,05 cm for XPS, as 11,54 cm for glass wool and as 8,44 cm for rock wool by using present worth analysis. Xopt is value that total energy cost is minimum at the end of the specific life time. The payback periods has been calculated as 7 years for EPS and XPS, 4 years for glass wool, 5 years for rock wool. When the results were evaluated, EPS was chosen as the insulation material applied to building external walls for Bursa. In the case of prepayment of the insulation cost or withdrawal from the bank with credit, the payback periods and the change in optimum insulation thicknesses for different life time were examined. Before the insulation is made, it has been evaluated whether depositing the insulation cost on the bank is more advantageous than the insulation application.