Effect of a one-dimensional approach in LCA on the environmental life cycle impact of buildings : multi-family case study in Flanders

The environmental impact of buildings is commonly quantified through life cycle assessment (LCA). Because of practical constraints (e.g. data limitations, timing, complexity), various simplifications are often made. However, the impact of certain simplifications is not clear. Due to the particular geometry of a building, the execution of renovation measures typically entails environmental impacts due to material and energy use at building envelope interfaces which are not considered in simplified LCAs. Hence, this paper examines the effect of a one-dimensional approach as simplification strategy on the environmental impact regarding material use and operational energy use for different renovation scenarios applied to a residential high-rise building. A simplified LCA is therefore compared with a detailed LCA that considers the real building design. First, the effect of linearly scaling the environmental impact based on a one square meter approach is confronted with the real building complexity. Then, the impact of neglecting thermal bridges on the operational energy use is analysed. Finally, both results are combined to evaluate the overall effect on the environmental life cycle impact. The simplifications entail an underestimation of the environmental material use, operational energy use and life cycle impact of 6–49%, 10–36% and 10–30%, respectively. The underestimation of the life cycle impact highly correlates with the operational energy use because of the significant contribution of the operational energy use to the environmental life cycle impact, namely 81–99%. As a result, the effect of simplifications concerning material use on the total life cycle impact is found to be negligible