Implications of façades’ visual reflectance for buildings’ thermal performance

Abstract

The surface properties of building façades have implications for thermal performance of buildings and might also influence outdoor thermal comfort conditions for pedestrians. A surface property, which is frequently used by building engineers and specially architects, is the visual reflectance. In this article, effects of façades’ visual reflectance on thermal aspects of building performance have been investigated in two parts. In the first part, the result of a field study is presented. The study explores the relationship between the visual reflectance of actual building façades and the corresponding surface temperatures. A number of buildings with diverse façade colors were selected. Surface temperatures were measured via infrared thermography. Façades’ visual reflectance was derived via simultaneous measurement of the illuminance on the façades and their luminance. Furthermore, incident solar radiation, ambient air temperature, and relative humidity were measured. The results of the field study display a non-random relationship between the building façades’ visual reflectance and their surface temperatures. The second part of the research involved the deployment of a calibrated simulation tool toward exploring the impact of façades’ visual reflectance on thermal performance of buildings. The results suggest that the magnitude of visual reflectance has little impact on indoor temperature and heating demand in case of façades with external insulation layer but may influence cooling loads in case of non-insulated buildings.