Abstract
The paper outlines a method of providing conventional open skylights with the ability to reject high-elevation light and accept low-elevation light. The angular-dependent transmission so provided is designed to allow skylights to be used in subtropical and tropical regions where overheating would normally limit this method of daylighting. An approximate theory of the angular-dependent transmission is derived and applied to calculate the time dependence of radiant input at various latitudes for clear and diffuse skies. The theory is compared with measurements on scale model skylights and shown to be adequate. The calculated transmission of the skylights is used with measurements of interior illuminance obtained in a scale model building to predict illuminances at other times and latitudes. This approach gave a useful measure of relative daylighting performance in actual buildings but not a reliable estimate of absolute illuminances owing to inadequate representation of the lighting performance of actual buildings by the simple scale model used. The angular-selective skylights have been installed in buildings in tropical Australia and the performance is being monitored.
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