Design of a Differentiated Daylight-Redirecting System and its Projected Performance Evaluation

This paper introduces the most popular technology and product in daylight reflection and its uses in façade areas. A window might be differentiated into its component parts, the higher daylight window and the lower view pane of glass applied with various transmittances. Visible light transmission may be higher in the upper glazing to increase daylight and lower in the view glazing to minimize glare. This might reduce the severe contrast ratio between the interior surfaces of the space and the brighter exterior view, with holding the higher performance of daylighting. Additionally, utilization of a lightshelf, the daylight-redirecting system, might improve the uniformity of natural light distribution in a space by attenuating the amount of daylight near the window area and relocating the intense sunlight into deep spaces. It is of limited usefulness under overcast sky conditions but clear skies with huge amount of sunlight dominate around whole year in Korea. Reduction of glare problem that exists at building perimeters is additional function of the daylight-redirecting system. Nevertheless, a difficulty in deciding the configuration of a lightshelf which is applied into on building facades still exists and it stems mainly from the fact a designer do not has the practical confidence on aesthetic impact and daylighting performance of the unfamiliar objects. This study aims to provide a set of designed images and quantitative daylighting data for the parametric types of a lightshelf. A daylighting analysis computer program, Lumen-Micro and scale models examine not only window treatment with glasses, but also daylight-reflection systems with lightshelve that serve to guide daylight.