Balancing the energy savings and daylighting performance of external perforated solar screens: Evaluation of screen opening proportions

Abstract

This paper aims at developing new types of external perforated solar screens by balancing between energy efficiency and daylighting. Three objectives were targeted: First, evaluating the energy saving potential of using solar screens in different geographic locations. Second: Examining the influence of screen opening proportions on illuminance values. Third, investigating recommended screen opening proportions for daylighting and their effect on energy efficiency. Two simulation software packages were used for the assessment: Energy Plus for energy performance and Radiance for daylighting performance. Results demonstrated the usefulness of utilizing external perforated solar screens in front of windows. The screens reduced energy consumption by 25% to 35% in a number of cities that lie between 14°N and 40°N. Their effectiveness was less obvious in cities that were further north. Daylighting performance investigations in a chosen geographic location (30°N) suggested that changing the screen opening proportion (horizontal: vertical) from 1:1 to 18:1 efficiently enhanced daylighting. Changing the proportion to 18:1 was recommended as it improved the deficient daylighting behaviour of the North direction, while resulting in a marginal effect on energy consumption. The 1:1 proportion was recommended for the Southern orientation. As for the East and West orientations, it is up to the designer whether the improvement of daylighting due to change in opening proportion is worth the compromise in energy consumption.