Indoor Daylight Performances of Optimized Transmittances with Electrochromic-Applied Kinetic Louvers

Abstract

Windows with low visible light transmittance (VLT) and g-values are preferred to reduce the building’s energy consumption. However, low VLT and g-value can create an unpleasant indoor daylight environment. A glass with freely adjustable VLT and g-value as required has been developed and is called smart glass. In this study, the recently developed VLT adjustable smart glass is targeted. Some studies were conducted on the VLT adjustment status of smart windows to create an appropriate indoor lighting environment. Although research on smart glass has been conducted through ecofriendly building certification systems such as LEED in the US, BREEAM in the UK, CASBEE in Japan, and GSEED in South Korea, it was pointed out that there is a limit to creating a uniformity. Therefore, the previous study analyzed the VLT conditions to create a minimal indoor daylight environment. The purpose of this study is to propose and analyze a louver-type electrochromic façade that can create a uniform indoor illuminance. A simulation method was used, and a range of changes in indoor illuminance that could be controlled through an electrochromic louver was derived. The simulation was performed using the Rhino 6′s Grasshopper program based on the Radiance engine. Electrochromic is a class of smart glass with high VLT variable range and durability. The conditions for deriving the optimal daylight environment according to the composition, VLT, and angle of the electrochromic louver were analyzed. The evaluation was made against the criteria of LEED v4.1. Data on the composition, VLT, and angle adjustment of the electrochromic louver that can obtain a high LEED v4.1 daylight score were derived, and organized in tables. Considering the composition and angle, it was found that the daylight environment of the electrochromic louver adjusted with a VLT of 25% to 45% was excellent in composition.