The assessment of daylight reflection from building envelopes

Abstract

Buildings could influence surrounding microclimate with their envelope designs. Reflective surfaces on the building envelopes could reflect daylight to the neighbourhood and cause problems such as glare and overheating. For the surrounding drivers, pedestrians and building occupants in the area, the reflected sunlight from the building envelope becomes the bright spot in their view which results visual discomfort or impairment. For building envelope designs, it is important to analyse the effect of daylight reflection to the neighbourhood at design stage. This could reduce the risk of environmental problems and minimize the consequences cost after construction. A software tool to evaluate the reflected daylight from building envelopes has been developed. It is implemented on parametric design platform GRASSHOPPER using RADIANCE as background simulation engine. As shown in the case study, using the tool, the form of the assessed building envelope could be analysed and the critical areas around the assessed building including roads, pavements and façades of neighbouring buildings are examined for potential concentration of reflected daylight. Rich information is recorded for the critical areas: annual reflected solar radiation, period with irradiance value above threshold, origin of the reflected daylight on the assessed building envelope, etc. This information could help designers to optimize the form of the envelope and make façade material selection. The tool shows potentials for architects to understand the impact of their designs and avoid potential environmental problems.