Software to determine the energy and light transmission of glass facades in conjunction with special daylight redirecting systems

There is a lack of angle-selective evaluation of sun protection devices in rating systems. In particular, the visual transmission of the blinds, which deals with visual comfort, has not yet been addressed. In this paper we look at a specific light distribution of the transmitted sunlight, to improve daylight illumination in the depth of the room under consideration of daylight autonomy. In order to make a qualitative assessment of shading devices and daylight systems, it is necessary to evaluate the technological structure of facades in their energetic consequence by a simultaneous evaluation of energy transmission, light transmission, room depth illumination and visual transmission with respect to latitude, orientation, climate, and sunshine hours. We developed a software simulator based on 3D ray-tracing to meet these needs. The software allows to define a glass facade in its optimum size (light entry surface) and its technological specifications, by calculating the quantitative functional diagram and supporting an optimization of glass assemblies and glass coatings in combination with light redirecting structures. This paper presents the development and features of the 3D ray-tracing simulation software, 3D-RayTracer. We have used the 3D-RayTracer to simulate light transmission. The results of two different daylighting systems are described (RetroLuxTherm 20 mm and RetroFlex introduced by company RetroSolar, developed and patented by Dr. Helmut Koester). The paper finishes by discussing energy savings and further development of the 3D-RayTracer.