Influence of Window-to-Wall Ratio on Calculation Methods for Building Surface Reflectivity

Solar radiation is the main source of building heat gains. Radiative heat transfer on building surface is not only the thermal environment analysis foundation, but also the primary task of calculating building heat gains. Reflectivity is an important calculation parameter for the radiative heat transfer process. In this paper, different building models are established by three building surface reflectivity calculation methods according to window-to-wall ratios. The building surface temperatures are compared, and the reflectivity-sensitive interval can be obtained. The results show that the influence of window-to-wall ratio, wall reflectivity, and seasons on three methods is obvious. When the wall reflectivity is small, the calculation methods are not influenced by four seasons. When the window-to-wall ratio is less than 0.5, the reflectivity-sensitive interval is [0.5, 0.9], and on other intervals, it is [0.1, 0.9]. Therefore, in order to make the radiative heat transfer simplified calculation more reasonable, different calculation methods could be selected according to the actual window-to-wall ratio. The research results provide a theoretical basis for the outdoor thermal environment analysis.