Comparative Performance of a Solar Screen With Respect to Perforation Ratio: Illuminance and Energy Saving

The objectives of sustainable building design are to provide the comfort to the occupants and to eliminate negative environmental impacts of its operations. In this regard, windows play a crucial role in saving energy used for electrical lights and enhancing the indoor visual environment. Excessive sunlight penetration through the windows could increase the heat gains and create the uncomfortable visual environment. Hence, external shading devices, such as solar screens, control the sunlight penetration and minimize its negative effects. The objectives of this research are to provide new insight into the impact of installing the solar screen on the indoor visual environment and heat gain through the window. Experimental measurements are conducted in extreme weather month and window direction, in June and for West facing façade window. Three design patterns of the solar screen were considered with perforation ratios of 12.5%, 25%, and 35%. Without a solar screen, the results show that there is a significant illuminance level variation in the indoor space, between 200 and 2250 Lux. However, if a solar screen with 12.5% perforation ratio is installed, the illuminance level in entire indoor space becomes uniform, it is maintained at 400 Lux during the daytime, and thereby visual comfort is attained. Additionally, the heat gain through the window is decreased by 52.8%, and the window is prevented from heating up during the daytime.