Analysis of dynamic louver control with prism redirecting fenestrations for office daylighting optimization

Abstract

Daylighting with redirecting complex fenestration system (CFS) may improve the indoor luminous environment. This study is to explore the strategies for controlling louver tilts of dynamic micro-prism film louvers corresponding to different solar incident angles, to optimize the work-plane illuminance (WPI) at the middle/back zone of the analyzed large-depth office, based on the simulation results of daylight filtering. To reduce the rotation frequency of the slats, several slat tilt angles were tested to adapt to the changes of different sun incident angles. The study compared the annual daylight performance and glare levels of the three CFSs with dynamic metal louvers, dynamic micro-prism film louvers, and micro-prism film, using the Five-phase method (5-PM). The results showed that the dynamic micro-prism film louvers combined with the proposed control strategy provided a better daylighting luminous environment, regarding the improved useful daylight illuminance (UDI) at inner space, and yielded less glare occurrence rates at space close to windows, compared with dynamic metal louvers and double glazing. Furthermore, the study proposed the combined dynamic louvers that consisted of micro-prism film slats and metal slats to reduce the possible glare on the premise and improve the indoor illuminance at the inner space. The simulation results showed that the combined dynamic louvers could reduce the discomfort glare occurrence rate by 68.9%, compared to the discomfort rate with double glazing at the front zone; UDI300-2000 lx of the combined louvers could be improved by 23%, compared with that of double glazing at the front zone. Compared with the metal louvers with similar low glare occurrence rate, the combined louvers could improve UDI100-300 lx at front/middle/back zones by 7.9%, 29.1%, and 2.9%, respectively, and UDI300-2000 lx by 40.0%, 11.7%, and 5.7% at these zones, respectively.