Optimization of Envelope Heat Gain and Interior Daylight Illuminance in Building Facade Design Under Reflectance Limitations: A Case Study of Office Buildings in Thailand

The popularity of using glass as the main building envelope material in commercial high-rise buildings has brought about numerous legal actions in recent years due to the widespread impact of the visible light reflectance of glass facades on the surrounding area. However, choosing suitable reflectance values for glazing the building facade remains a viable solution to lessen envelope heat gain and reduce cooling energy demand. Despite this, maximizing daylight is essential to maintaining healthy vision and the circadian rhythm of the building users. As a result, finding the optimal solution for envelope glass property selection to provide minimum heat gain through the building facade and maximum indoor daylight became a great challenge. The experimental research is conducted to identify the relationship between overall thermal transfer value (OTTV) and useful daylight illuminance (UDI) and to find suitable enveloped glass performance properties. Two typical high-rise office buildings in Thailand with a square-shaped and a rectangular-shaped floor plan are selected as case studies. BEC, a web-based program developed by Thailand’s Department of Energy Development and Efficiency, and Rhinoceros 6, along with Grasshopper, Ladybug, and Honeybee plugins, are used to calculate the OTTVs and transmitted visible light within the building, respectively. The results show that the maximum proportion of the building area that passes UDI requirements while in accordance with OTTV criteria is 23% and 26% in the square-shaped plan and the rectangular-shaped plan, respectively. These cases are with the WWR 80 and with glass performance values of SHGC 0.2, VLT 31%, and U-value 1.62 W/m2K.