The architectural application of Altmann linkage as a light shelf

Abstract

Daylight and its penetration in a room are significant concerns in architectural design. Light shelves are necessary to control daylight on fenestration. In the literature, there are many daylight controller systems such as light shelves. This paper presents the possibility of using Altmann linkage as the basis of constructing such a light shelf in rectangular form. It is basically a horizontal or inclined device, having high reflectance on the upper surface to control and redistribute daylight, placed above the eye-level in the fenestration system. The performance of a light shelf varies according to its dimensions, distance to window sill, distance to window head, its rotation angle and orientation in terms of daylight efficiency and visual comfort. It is also used to provide shading. This system can be internal or external and being static or movable. A light shelf presents its maximum efficiency in south facing façades receiving higher direct sun incident angles in medium latitudes of northern hemisphere. The aim of this study is to explain the design process of an adaptable Altmann light shelf including dimensioning the links in a rectangular form, calculating rotation angles, modelling this device in Relux to test its daylight performance. Regarding the Altmann geometries, three variations are set while changing its distance to window sill. The aim is to test illuminance and uniformity. Relux calculates illuminance and uniformity at four significant dates and three chosen hours for each one, to obtain the best design.