Review Paper: Innovative daylighting: Review of systems and evaluation methods

Abstract

New day lighting systems such as the light pipe, light shelf, mirrored louvres and prismatic glazing have two main objectives: to bring daylight deeper into a space, and to control and distribute direct sunlight so that this can be used as an effective working illuminant. While a large number of devices has been proposed, little has been done to show rigorously whether they do in fact save energy or improve the internal environment. This paper describes the available systems and gives initial design guidelines. Sunlight-only systems appear to be inappropriate for the UK; enough diffuse sky light must enter the space and this can be checked using the average daylight factor method in the CIBSE Applications Manual Window Design. Whatever system is chosen, it should cope with the sun's movements; it is unreasonable to expect occupants to make adjustments continually. Good control of electric lighting will be required and maintenance needs to be carefully planned. Further work is still necessary before the cost effectiveness of these systems can be evaluated. The paper outlines photometric and calculation techniques being developed to assess these new options in daylighting design.