Environmental emissions in building construction: Two case studies of conventional and pre-fabricated construction methods in Australia

Emissions at the construction stage seem to be getting a lot of attention in the research area for its relative significance over shorter time spans. Applications of various construction methods are recognised as one of the options to minimise emissions at the construction stage of a building. The focus of this study is to compare emission distribution of different construction methods. Two case studies of conventional and semi pre-fabrication construction methods in Australia are employed to compare this emission variation of adopting different construction methods. It sets a system boundary of embodied emissions from building materials, emissions from construction equipment, transportation of building materials, pre-fabricated materials and construction waste. Quantitative models are developed to compute both greenhouse gas (GHG) and non-GHG emissions. An impact assessment was also carried out to examine the relative importance of impacts at global, regional and local perspectives. The case study results indicated that adopting pre-fabrication method offers a GHG emission reduction of 1.7% while an increase of non-GHG direct emissions by 0.9 to 3.5%. Global Warming Potential (GWP) remained the highest impact category for all the perspectives considered, with an overpowering 86.8% contribution from global perspective. However, this relative importance is reduced to 52%, with a relative increase in Eutrophication (EP) and Photochemical Oxidant Formation Potential (POFP) up to 21.74% and 27.14% at regional and local perspective. Emission increase due to transportation shows a relative increase in POFP potential for pre-fabrication. These results signify that non-GHG emissions should be given importance at regional and local perspective when using pre-fabrication method in construction.