Simultaneous optimization of office building facades in terms of both energy consumption and transparency in hot arid climates, analysed on the example of Cairo

Abstract

Since the early days, buildings forms, types of construction, and development were closely responding to the local climatic conditions. However, the technical innovations during the last 150 years and the calls of modern architecture to transparency drove the building sector towards the extensive usage of glazed facades in commercial buildings and to the adoption of the international style buildings. Those building models can only function through the extensive intervention of technical equipment to guarantee the desired internal comfort conditions at any place of the world with the corresponding massive energy input, owing to the poor thermal performance of glazing and its selective property with respect to radiation permeability (greenhouse effect). Unfortunately, this situation is very apparent in Cairo. Contemporary commercial buildings are being increasingly designed and constructed based upon highly glazed building models originally conceived in, and for, countries with moderate climates. Such architecture is totally maladapted to the hot-arid climate, especially with the extensive solar radiation and the relatively high summer temperatures. However, on the other hand, transparency provides crucial psychological values and benefits to the occupants. It affects their comfort, sense of well-being, and affords them view and natural light. View provides the occupants with visual amenity, access to environmental information, relief from claustrophobia and monotony, and recovery from daily stress. While natural lighting has a direct influence on mood and cognition, and influences the production of hormones, it also regulates motivation, and improves productivity in the workplace. In addition, the proper use of natural day-light decreases the energy used for lighting and improves the environmental quality indoors. The research work aims to elaborate a scientific methodology in order to optimize the office facades configurations in hot-arid climates, analyzed on the example of Cairo. The research methodology is based on investigating the adequate balance between two critical, and at the same time conflicting requirements or tasks, which are: First: To provide the required level of transparency that provides the occupants with their psychological sense of satisfaction and general well-being. Second: To reduce the total energy consumption of the building through an energy-efficient concept based on a proposed solar protection strategy. Through a series of parametric analysis processes of the energetic performance of the selected solar protection variants (represented by their total annual energy consumption per square meter) with their corresponding visual quality (represented by their view index measures), the research provides an optimized definition for the configuration of office facades. The optimized façade designs achieved the required balancing ratio that gives the occupants psychological satisfaction and general well-being. The research proposes an Energy-Transparency Balancing Factor (ETBF) in order to compare and differentiate between the findings of these optimized configurations.