Thermal performance of different exterior wall structures based on wall orientation

Abstract

Heat transfer from opaque walls of buildings is very important for energy saving and providing thermal comfort in different climates. In this study, insulation models of opaque walls with different orientations and external, internal and sandwich materials were numerically analyzed in terms of their time-dependent thermal behaviors. The one-dimensional transient heat conduction equation was solved via the implicit finite difference method for summer and winter conditions and northern, southern, eastern and western orientations. Meteorological data for cities in Turkey with different climates, i.e., Ankara, Erzurum, İstanbul and İzmir, were used in these calculations. When the outside boundary conditions were defined by using January and July monthly averages of the daily data; the inside air temperature was assumed to be 20 °C and 24 °C in winter and summer. The results indicated that sandwich wall insulation produced more convenient heat loss and heat gain for each climate and direction. The standard deviations of the heat transfer values for the different directions were larger in summer than in winter because of the solar radiation effect. The numerical calculations for the sandwich wall applications were carried out for different insulation thicknesses namely 0.15 m and 0.25 m, and for an uninsulated wall; the results were also compared with Turkish directive on the thermal insulation of buildings, TS825 taken as a reference condition. Compared with the insulation thickness calculated based on the TS825, the heat loss and gain values could be decreased by up to 65% and 80% for the worst winter and summer conditions.