A New Daylight Glare Evaluation Method

Abstract

Ergonomic design of workplaces requires a proper method for predicting glare to promote visual comfort. Only a few formulae have been proposed for discomfort glare of daylight origin, and they are inadequate in real daylight situations. No standard monitoring procedure is available to establish a basis for daylight glare evaluation on a comparative basis. This paper introduces a new glare evaluation method consisting of a standard monitoring protocol and advanced formulae. The method has been tested against the existing glare evaluation system proposed by Chauvel using Radiance, a lighting simulation program. The two systems are compared here in terms of formulations and their performance when tested on different types of window transmittances over the whole year. Given reliable results, the new DGIN procedure was coded into a small program and incorporated with Radiance to calculate the luminance values and to compute daylight glare indices. Also glare from another daylighting control strategy—the light shelf—was investigated. The new method is sensitive to the vertical illuminance and thereby to the source illuminance, and appears to yield sensible and consistent glare values; the higher is the source luminance, the worse will be the glare sensation. The method was developed with the hope that architects and lighting designers would adopt it as an easy and reliable method for evaluating discomfort glare from daylight. The future work, which is an ongoing research, is to create the use of scientific-knowledge computational tools in the later stages of design in an effort to provide optimum choices of daylighting design with respect to light level and glareusing the new glare algorithm.