Hanan Sabry

Daylighting Efficiency of External Perforated Solar Screens: Effect of Screen Axial Rotation under Clear Skies

This paper aims at developing solar screens for use in front of windows under the clear desert skies. These external perforated panels revitalize a traditional solution named “Mashrabeya”. They contribute to sustainability through utilization of natural light. In this paper, series of experiments were conducted using Radiance software. The impact of solar screen axial rotation on indoor daylighting of a residential setting was investigated. The effectiveness of the axial rotation was demonstrated. Screen influence on daylighting was strongly dependent on the orientation of the window and time. Illuminance adequacy was tested. The North and South orientations with upward and downward horizontal axial rotation were most affected when the rotation angle increased from 0° to 30°, especially in the summer season. In the East, the winter season was the most affected by the rotation. As a response to changing the rotation angle, a linear increase relationship was observed in all orientations.

HIGH PERFORMANCE FACADES: THE EFFECT OF SUN BREAKERS ON DAYLIGHTING PERFORMANCE AND ENERGY CONSUMPTION IN SOUTH ORIENTED OFFICE SPACES

Daylighting is considered one of the main passive strategies for enhancing indoor spaces quality. Shading device is usually used to prevent excessive sunlight from delivering into the building, especially in clear-sunny sky environment. The use of a per-formative shading device can help in reducing both cooling and lighting loads, as well as improving the quality of the space. Nevertheless if such devices are not designed with care it may cause to admitting more sun rays than needed or result into poor daylit spaces. Sun breakers are believed to enhance the performance of southern faced spaces, as it provides protection from the excessive solar rays which have direct effect on the cooling loads. This paper investigates the effect of using sun breakers on both daylighting and energy performance. Year-round daylighting and energy simulations were conducted for a south oriented office space, located in the city of Cairo, Egypt. Diva-for-Rhino a plug-in used to interface Radiance and Daysim was used for calculating the annual Daylight Availability of the space. While Viper another plug-in for rhino and used to interface Energy-Plus was used for annual energy consumption simulations. Sun breakers with different settings and parameters were compared and the results were analyzed for achieving the needed balance. Results showed that the performance of sun breakers is tremendously related to its position, depth and rotation angle. The daylighting performance could be significantly enhanced; the ‘Daylit’ area percentage can reach more than 72% of the space, while the savings in the annual energy consumed had also reached up to 34%. The results also showed that there is a satisfactory balance between the daylighting solutions and the thermal ones.