Estimation and comparison of environmental emissions and impacts at foundation and structure construction stages of a building - A case study

Previous studies have seldom investigated the effects of direct emissions at different stages of a building construction. This study aims to estimate and compare direct and indirect emissions and environmental impacts at foundation and structure construction stages of a building using a case study. The case study is multi-storey commercial building construction with concrete framing. A process based methodology is developed to estimate emissions from seven sources that contribute to both greenhouse gas (GHG) and non-GHG emissions. An impact assessment is also carried out to compare the environmental impacts for different stages of construction from global, regional and local perspectives. The results highlight an overpowering indirect GHG contribution of 89% from material embodied emissions at the structure construction stage. Direct GHG emissions at the foundation construction are prominent with a contribution of 12.7% and 13.4% for emissions from equipment usage and transportation respectively. Nitrous Oxides (NOx) and Carbon Monoxides (CO) are recorded as the most prominent non-GHG emissions. The results were further analysed based on four scenarios corresponding to direct and indirect emissions. The results signified a GHG emission reduction of 12% can be achieved by adopting sustainable materials such as fly ash and blast furnace concrete. The impact assessment results illustrate a large contribution to global warming potential (GWP) with a value of over 98% for the construction stage from the global perspective. This large contribution from GWP is reduced to 60% and 57% with relative high contributions from Photochemical Oxidation Potential (POFP) with 26% and 34% at regional and local levels. The scenario analyses on direct emissions highlight the importance of resource utilisation in reducing impacts at local level. The results indicate that identification of the significant emission sources and impact categories at different construction stages, prior to im