The effect of surface reflectance distributions on average daylight factor values in atrium buildings

The aim of this research was to study parametrically the effect of different distribution patterns of atrium wall reflectances on average daylight factor values in the well of a square, four-sided, top-lit atrium model that was placed inside an artificial sky. The artificial sky replicated the luminance distribution of a CIE overcast sky. To achieve the variability in reflection distribution, the atrium surfaces were painted in alternating bands of white and black horizontal stripes. For each of the experiments the widths of these bands were altered but the overall split between white and black bands was always maintained at 50%. Experiments were also conducted for atrium wall surfaces painted all black (0% wall reflectance) and all white (100% wall reflectance). This study was able to investigate the impact on ADF values in atria of more realistic distributions of light reflecting surfaces. Results from the study showed that the ADF values on the floor of the atrium, compared to the standard calculated ADF, were affected by the reflectance distributions of the atrium surfaces. Wide bands of different reflectances displayed the largest variations. For narrow bands the different reflectance distributions did not affect the ADF levels as much. The results of this study demonstrate importance of the reflective properties of the atrium surfaces and the variations in reflectance distributions on the daylight reaching the atrium floor.