Simple method for determining daylight illuminance in a heavily obstructed environment

Daylighting has long been recognized as an important issue in architecture. In Hong Kong many buildings are constructed close to each other and hence the external environment plays a significant role in building designs. Recently, vertical daylight factor (VDF) has been used as a criterion to justify the provision of natural lighting in buildings. This paper studies the calculation approach of VDF in a heavily obstructed environment. The techniques for determining the sky component and the reflected daylight from surrounding buildings and ground surfaces are described. Calculation tools in the form of simple equations and diagrams through computer-simulation analysis were established. The performance of the proposed method was evaluated against the daylight illuminance obtained by other independent computer simulations. It was found that predictions from the proposed approach were in good agreements with those produced by simulated results. The findings provide architects and building designers with a simple method for estimating the daylight illuminance at early design and planning stage.