A study on the accuracy of daylighting simulation pf heavily obstructed buildings in Hong Kong

Hong Kong is the most densely populated city in the world. The Building Regulations of Hong Kong pre- scribe a minimum distance between buildings for light- ing and ventilation. Lately, designers are testing the prescribed requirements with a  performance based ap- proach using computational simulations. Doubts have been cast as to their validity and accuracy. This study compares results obtained by on-site measurements, calculation  and simulated results using Radiance and Lightscape. The study concludes that both Radiance and Lightscape over estimate daylight availability by up to 50% under conditions of high external obstruction. A work around method is suggested.