Reflectance distributions and vertical daylight illuminances in atria

Abstract

In this study parametric changes were made to the distribution of the reflectances of diffuse vertical surfaces in the wells of model square atria placed in an artificial sky. The effects of these changes on the vertical daylight levels at various heights for central positions were examined. Painting the atrium surfaces with alternating, equal width bands of white and black matt paint created the reflectance distribution variability. The widths of the bands were gradually reduced, although the 50:50 black to white ratio was kept constant. The different distributions of reflectances were found to have very little effect on vertical daylight factor and internally reflected component values low down in the atrium well. For some of the higher measurement locations large differences were observed between the different reflectance distributions. Generally, as the bands became narrower and more numerous the daylight levels converged towards values that would be predicted from standard formulae using the area-weighted reflectance of the atrium.