The impact of façade design on daylighting performance in office buildings :the case of Beirut, Lebanon

Abstract

An energy shortage arose in Lebanon during and after the civil war (1975-1990).62% of the national electricity generation is consumed by building stock, of which 70/0 is consunled in the conlnlercial sector. Given the acute shortages and increased consumnption, there is a need to rationalise the use of energy in the building sector. There is growing evidence that buildings which adopt passive design solutions, such as daylighting and natural ventilation, have good energy performance and show higher occupant satisfaction. Daylighting can be a good contributor to energy efficiency in the buildings of Beirut. where the climate is typically Mediterranean and daylight is available 12 hours per day on average. During the last century, the development of façade configurations and the widespread adoption of international design trends in Beirut, particularly in office buildings, changed the energy consumption pattern. The lack of any building regulations that considered the potential of daylighting led to an underestimation of the impact of façade design on the internal environment and building energy behaviour. The aim of this study is to develop design guidelines for office building façade configuration and plan morphology that will contribute to the best use of daylighting, with associated potential energy savings, in Beirut. To achieve this, the study has three main parts. Firstly, the literature relating to daylighting design principles, glazing façades and human comfort in workspaces is reviewed in order to identify design parameters and variables that are significant for daylighting performance in office buildings. Thereafter, the seven historical phases of architectural development in Beirut are identified. Examples of office buildings from each phase are evaluated for their daylighting efficiency, in accordance to four parametric levels describing the 'Building Shape, 'Window/Façade' and Window/Office' relationships, and the 'Shading Devices' used. Finally, the lighting behaviour of 14 selected case studies is simulated using ADELINE. Electrical lighting consumption and the possible savings due to the implementation of different lighting control strategies are calculated. The simulation outputs are validated by empirical energy data. Finally design guidelines for the best practice in the office buildings of Beirut are produced, by coupling the evaluation of daylighting design variables and energy savings measures.