Prediction of reflected solar dazzle from sloping facades

Abstract Glare or dazzle can occur when sunlight is reflected from a glazed facade. For vertical facades this problem usually occurs only when the sun is low in the sky; but some types of modern design incorporate sloping glazed facades which can, under certain circumstances, reflect unwanted high altitude sunlight into the eyes of motorists, pedestrians and people in nearby buildings. This paper presents, for the first time, a method which can be used at the design stage to calculate whether such solar dazzle will be reflected from a proposed building facade. From simple input data the times (if any) of year at which reflected dazzle could occur, and the total number of hours for which sunlight would in practice be reflected, can both be calculated.