Effects of shade trees on illuminance in classrooms in the United Arab Emirates

This study investigated the potential of shade-trees to improve lighting conditions in the indoor space of a standard classroom in the United Arab Emirates (UAE) using computer simulation with the Radiance program. Shade trees are defined as selected suitable types of trees using certain criteria (i.e. evergreen, proper canopy density, proper height, growth in extreme hot climate conditions, safe roots) based on literature survey and consultation with landscape experts. It focuses on analysis of illuminance levels at desk locations (task) inside a standard classroom oriented to the North, East, South, and West for the selected critical times that are relevant to the locality. An initial group of simulation runs was done at the outset to choose proper tree spacing. The dependent variables are illuminance level and illuminance range resulted from manipulating two independent variables, shade tree type and orientation. The simulation runs includes a base case with no shade trees against other improvement cases with shade trees. The findings show the significance of the shade trees for improved lighting distribution and quality. This is evident in the reduction of illuminance ranges throughout the classroom as it is the case with the Neem shade trees at 2 m providing the lowest range from 125-570 Lux on front of the window and from 130-498 Lux on front of the wall. Yet, some reduction in the overall levels of illuminance is experienced (18-31% reduction for North orientation; 87-96% reduction for other orientations) and an increase in the estimated operating hours of electric lighting. Finally, some passive methods such as high strip windows and roof monitors were recommended to compensate for the illuminance reduction, rather than using electric lighting.