The Impact of Tilting Northern Open Space Wall on Daylight Performance of Residential Buildings

A northern open space (NOS) is built in some residential buildings to enhance daylight performance of indoor spaces which do not access to yard or other open spaces. Compliant with the urban standards of Iran, NOS must be partitioned from the adjoining yard by a tall wall. Economically, for increasing the usable residential area, the NOS width is often limited to the minimum of urban standards. A typical residential building located in the densely-built Mardavich area was selected as a case. This paper, using daylight simulation, calculates and compares the impact of two variables on the illuminance level of indoor spaces: the NOS width and the angle of NOS southern wall. For this end, the illuminance levels of the indoor space were measured and at different conditions: three widths of NOS (2, 3, and 4 m) with the vertical southern wall, minimum width of NOS (2 m) with four tilted southern walls (5, 10, 15, and 20 degree). The daylight simulation at winter solstice was conducted for estimating the minimum daylight level and the daylight simulation at summer solstice was conducted for predicting the potential glare. The results of this study show that tilting the southern wall of NOS (facing to indoor space), allocating a smaller area to the NOS, increases the total usable space area of residential buildings and improves its daylight performance; Based on these results, this paper recommends a novel strategy for architects to enhance the daylight performance of NOS by creating semi- funnel shape for NOS.