Authors: A. Sherif, R. Arafa and A. El Zafarany
External perforated solar screens were typically used to block direct solar radiation in hot climates, where cooling loads are significant. Previous research demonstrated that using solar screens to protect windows reduced energy use by 30%. Protecting the façade walls with solar screens in a way that covers both the fenestration as well as the walls may increase the energy savings. This could prove useful in the retrofit of existing buildings where solar screens can be installed externally on the façade walls to assist or substitute wall insulation. This paper aimed to quantitatively define the energy saving potential of utilizing external perforated solar screens for shading the solid parts of façade walls. This was compared to the energy saving resulting from wall insulation. The paper also aimed at understanding the behavior of solar screens as a shading system for solid walls. Simulations were conducted using the EnergyPlus Software. Two solar screen perforation percentages were tested on insulated and un-insulated wall configurations in a typical residential building assumed to be located in hot climates of the cities of Cairo, Egypt and Ahmadabad, India. Research results demonstrated that using external solar screens for wall shading achieved significant energy savings in comparison with wall insulation. In the semi-arid climate of Ahmadabad, the energy saving was 14%, which exceeded wall Insulation. In the hot-arid climate of Cairo, wall shading saving was 11%, which was comparable to wall insulation. Results also showed that using denser screens for wall shading yielded better results. Combining wall shading with thermal insulation improved energy performance. Combining wall shading by a solar screen having a 40% perforation in association with a 10 cm insulated wall resulted in energy savings reaching 22% and 25.5% in the tested cities respectively. However, window shading proved to be more effective than wall shading and insulation.
Keywords: Shading; Solar Screen; Desert