Impacts of Building Forms and Light Reflectance of Building Glass Façade on Visual Discomfort of Surroundings

Abstract

High-rise buildings have been commonly built in Bangkok, Thailand over the last decade. Currently there is the Thai building energy code, which is related to building envelop designs that govern both building façade reflectance and total heat transfer through the exterior envelop or OTTV. Since the code has been developed and recently announced with more intensive regulations, building façade designs with glass envelop have become an important issue. This research attempts to develop a guideline to assess the environmental impact of the reflection of glass buildings on the visual discomfort from glare towards neighboring buildings. The key parameters of the experiment are shapes of building and visible light reflectance of glasses. In this study, five building shapes were defined with various light reflectance, which are 5%, 10%, 15%, 20%, and 27%. These case studies were simulated using Rhinoceros + Grasshopper software to evaluate illuminance level and daylight glare probability (DGP) value. Five thousand four hundred simulation cases were performed. The results showed that if the reflection from the glass building projects directly into the eyes of observers, regardless of the building’s shape and reflectance, the calculated DGPs values were always higher than the imperceptible glare level (DGP < 0.35). To avoid lawsuits between building owners and neighbors after the building construction, the environmental impact assessment should be conducted on a case-by-case basis. The concern cases are buildings with a concave shape design or a tapered tall building with fully covered glass facade and without sun shading devices to reduce reflection. The recommendation is to assess the direction of the reflected light to determine the location of the point that will be severely affected first. Therefore, the DGPs value from that location should be calculated and the impact assessment should be performed in order to find design solution measures. Initial study suggests that the reflection impact be reduced by using solar shading on glass facades.