PLEA2012 - 28th Conference, Opportunities, Limits & Needs Towards an environmentally responsible architecture Lima, Perú 7-9 November 2012 Utilization of Combined Daylighting Techniques for Enhancement of Natural Lighting Distribution in Clear-Sky Residential Desert Buildings Hanan SABRY 1 , Ahmed SHERIF 2, Mahmoud GAD ELHAK 1 1 Department of Architecture, Faculty of Engineering, Ain Shams University, Cairo, Egypt 2 Department of Construction and Architectural Engineering, The American University in Cairo, Cairo, Egypt ABSTRACT: Desert buildings are exposed to clear sunny skies almost all year round. Solar rays penetrate into spaces creating a non-uniform daylight distribution and high solar heat gain; affecting both visual and thermal comfort. This paper addressed the usefulness of combing solar screens and light shelves for achievement of efficient daylight performance in a residential living room space. The objective was to harvest daylight while diffusing direct sun rays, thus, reducing artificial lighting and energy use. Simulations were conducted using the Diva-for-Rhino plug-in to interface Radiance and Daysim for the evaluation of annual Daylight Availability according to the minimum required illuminance value. The impact of combined design alternatives and techniques was tested for the purpose of increasing the “daylit” and reducing the “over lit” and "partially daylit" areas. Results showed significant improvements in daylight distribution in all orientations. In the North and South orientations, more than one combined design attained the highest value for "daylit" area, reaching 95% and 85% in these orientations respectively. While in the East orientation, only one combination achieved this goal where a 67% "daylit" area was reached. Conclusions recommended alternative means of combining solar screens with light shelves for improvement of daylight distribution for each orientation. Keywords: solar screen, light shelf, daylight availability, simulation , clear sky desert environment INTRODUCTION The growing demands for healthier and more energy efficient buildings have increased the attention to provision of daylight in residential buildings. In desert dominated countries buildings are exposed to clear sunny skies almost all year round. Solar rays penetrate into spaces creating a non-uniform daylight distribution and high solar heat gain; affecting both visual and thermal comfort. Solar control systems such as solar screens could improve the performance daylight in the building interiors of these countries. The objective is to harvest daylight while diffusing direct sun rays, thus, reducing artificial lighting and energy use. One of the traditionally used solar control systems in the Middle-Eastern countries is the “solar screen; named “Mashrabeya” or “Rawshan” in Arabic. These were typically made of fixed perforated panels composed of a lattice of wooden cylinders or other shapes connected with wooden joints [1]. Kim, T., et al. [2] explored external fixed shading devices that were in a way similar in concept to these solar screens. They improved the daylight performance and provided excellent view in comparison with conventional venetian blinds. Aljofi, E., [3] demonstrated that daylight distribution was improved by use of the “Rawshan” screens in certain tested spaces. The highest value of reflected light contribution was found in the central zone for all shapes of solar screen cells. In addition, rounded shaped cells were found to provide lower values in comparison with other shapes. The impact of seven shading devices on daylighting was investigated by Dubois, M.-C. [4] using Radiance simulation at three specific times on three sunny days. Also Wong, N., et al. [5] discussed the effect of seven different types of external shading devices on daylight flow into building by using the Lightscape for daylighting simulations. Moreover, Alzoubi, H., et al. [6] evaluated the effect of different types of solar shading devices on energy consumption for southern exposure facades. He estimated the energy consumption attributed to lighting spaces for three common positions of shading devices (vertical, horizontal and 45° tilted horizontal shade). The paper concluded that there is an optimal orientation for shading devices that keeps the internal illuminance level within acceptable range with the minimum of solar heat gain. Claros, S.-T. et al. [7] investigated the influence of different materials of light shelf on daylighting performance using physical scale modeling. It is apparent that most of the related previous studies addressed different design aspects of shading and daylighting systems and their influence in controlling solar radiation and natural light potential indoors. Very little research addressed the combined effect of changing their parameters at the same time especially in clear sky desert environments. This paper aims at enhancing daylighting performance in a typical residential living