Life cycle assessment of energy and CO2 emissions from cast in-situ and industrialised building systems

Abstract

The conventional cast in-situ (CIS) building construction method is predicted to produce and generate large quantities of waste and carbon emission to the environment. On the contrary, Industrialised Building System (IBS) has shown great potential as a green construction method and in promoting environmental building sustainability. This study evaluated and compared the environmental performance (energy and CO2 emissions) of residential buildings in Iskandar Malaysia constructed using the CIS and IBS methods via a life cycle assessment (LCA). In addition, the trends in energy consumption and CO2 emissions during the buildings’ operational phase were also identified as this phase had the largest proportion of energy demand and CO2 emissions. This study also analysed the patterns and hotspots of energy use and CO2 emissions throughout the building life cycle for both case studies. In the first phase of this study, a functional unit of 1 m of built-up area was identified throughout the building life cycle. The system boundaries were then set from an identified input-output framework from the cradle-to-gate LCA of residential buildings covering the assembly phase, the use phase, and the disassembly phase. The input-output framework of the LCA building processes was identified as an input flowchart for further analysis in GaBi software. The results indicated that IBS residential buildings have a more positive environmental impact than the CIS residential buildings. The CIS building and the IBS building had an 85.17 percent difference in energy consumption and an 87.17 percent difference in CO2 emissions throughout a building life cycle of over 50 years. The identified hotspots during the material stage provided a better understanding of the contribution of energy and CO2 emissions, especially by precast concrete, reinforced steel, and concrete. Apart from building performance affecting the building energy and CO2 emissions during the operational stage, household characteristics, electrical appliances, and resident behaviour are also contributing factors that cannot be neglected. The dramatic reduction in environmental impact during the operational phase of the IBS building is not only interrelated with the application of the building materials used (precast concrete), but also the integration of the LCA methodology into the design phase, such as the orientation of the building facing North-South, further supporting the development of sustainable buildings. This analysis also provides concrete results supporting the adoption of IBS building construction to achieve low-energy and lowcarbon residential buildings in Iskandar Malaysia.