On Calculating the Effects of Daylighting in Interior Spaces

Abstract

A technique is described for calculating illuminance, equivalent sphere illumination (ESI), and the indirect effect on visual comfort probability due to the presence of daylighting in interior spaces. Finite Fourier series techniques are used to generate functions that describe the effects of differential elements of windows or skylights. The form of these functions allows for easy integration with resulting simple form to the final equations and also provides for computationally efficient algorithms. The equations are applied to the determination of the interreflected and direct components of illuminance and ESI due to windows or skylights. It is shown how to account for the effects of drapes, shades and overhangs on windows. Further, it is shown how to efficiently treat skylights that are recessed up into wells.