A benchmarking analysis of sunlight and daylight availability in a highly dense urban area in southern China

The availability of daylight and sunlight in dense cities has increasingly received attentions. This article presented a benchmarking analysis of daylight & sunlight availability in six urban residential layouts at Guangzhou in southern China. As representatives of old or new towns, these layouts were achieved using local regulations. The benchmarking system was built based on an urban building under various levels of obstruction (horizontally infinite length). Daysim (Radiance) and T-sun were applied to calculate daylight illuminance and sunlight hours at building facades, respectively. Some findings were achieved as follows: 1) For sunlight availability, significant effects of urban layout and orientation can be found in both towns. Most layouts achieved similar sunlight hours as an urban building with high and heavy obstructions, while several southeast-oriented and southwest-oriented layouts had the values like a building with the medium obstruction. No clear differences of sunlight hours can be found between southeast and southwest orientations. 2) For daylight availability, most buildings in both towns had similar frequencies of proper vertical illuminance as an urban building with the medium obstruction. However, the frequencies of excessive vertical illuminance significantly varied in layout, façade position, and orientation and corresponded with the values of an urban building with different obstructions. Effects of layout were found to be clear at low and middle façade positions, while significant effects of orientation were only found at higher façade positions. 3) Generally, a daylighting analysis using the dynamic climate-based model could achieve more practical results than the approach of sunlight hours.