Global warming implications of facade parameters: A life cycle assessment of residential buildings in Bahrain

Abstract

On a global scale, the Gulf Corporation Council Countries (GCCC), including Bahrain, are amongst the top countries in terms of carbon dioxide emissions per capita. Building authority in Bahrain has set a target of 40% reduction of electricity consumption and associated CO2 emissions to be achieved by using facade parameters. This work evaluates how the life cycle CO2 emissions of buildings are affected by facade parameters. The main focus is placed on direct and indirect CO2 emissions from three contributors, namely, chemical reactions during production processes (Pco2), embodied energy (Eco2) and operational energy (OPco2). By means of the life cycle assessment (LCA) methodology, it has been possible to show that the greatest environmental impact occurs during the operational phase (80–90%). However, embodied CO2 emissions are an important factor that needs to be brought into the systems used for appraisal of projects, and hence into the design decisions made in developing projects. The assessment shows that masonry blocks are responsible for 70–90% of the total CO2 emissions of facade construction, mainly due to their physical characteristics. The highest Pco2 emissions factors are those of window elements, particularly aluminium frames. However, their contribution of CO2 emissions depends largely on the number and size of windows. Each square metre of glazing is able to increase the total CO2 emissions by almost 30% when compared with the same areas of opaque walls. The use of autoclaved aerated concrete (AAC) walls reduces the total life cycle CO2 emissions by almost 5.2% when compared with ordinary walls, while the use of thermal insulation with concrete wall reduces CO2 emissions by 1.2%. The outcome of this work offers to the building industry a reliable indicator of the environmental impact of residential facade parameters.