The design and evaluation of three advanced daylighting systems: Light shelves, light pipes and skylights

We present results from the design and evaluation of three advanced daylighting systems: a light shelf, a light pipe, and a skylight. These systems use optical films and an optimized geometry to passively intercept and redirect sunlight further into the building. The objectives of these designs are to increase daylighting illuminance levels at distances of 4.6-9.l m (15-30 ft) from the window, and to improve the uniformity of the daylight distribution and the luminance gradient across the room under variable sun and sky conditions throughout the year. The designs were developed through a series of computer-assisted ray-tracing studies, photometric measurements, and observations using physical scale models. Comprehensive sets of laboratory measurements in combination with analytical routines were then used to simulate daylight performance for any solar position. Results show increased daylight levels and an improved luminance gradient throughout the year-indicating that lighting energy consumption and cooling energy due to lighting can be substantially reduced with improvements to visual comfort. Future development of the designs may further improve the daylighting performance of these systems.This research was funded by the California Institute for Energy Efficiency (CIEE), a research unit of the University of California. CIEE is a consortium of the CPUC, the CEC, and California utilities including LADWP, SCE, SCG, SMUD, and PG&E. Publication of research results does not imply CIEE endorsement of or agreement with these findings, nor that of any CIEE sponsor. Additional related support was provided by the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Building Technologies, Building Systems and Materials Division of the U.S. Department of Energy under Contract No. DEAC03-76SF00098