Illustration of methodological challenges in energy and environmental assessment of buildings

A life cycle approach (LCA) is now commonly used for the environmental assessment of buildings. However, different methodological rules are currently found in the literature to estimate the energy and LCA balance for the use stage e.g. from an annual assessment to a one hour time step assessment. Another critical issue is related to the assessment of new low energy buildings equipped with on-site renewable energies. In this study, first, the consequences of using different Life Cycle Inventory (LCI) calculations for the electricity mix are analysed. Then, the consequences of using different allocation rules for the on-site renewable energy produced by PV panels are assessed. The results on a single individual house showed that the use phase results are very sensitive to the allocation rules. Regarding the temporal aspects, this study highlights the differences between dynamic and static approaches for both energy and LCA calculations. Finally, recommendations are given to improve the reliability of building LCA tools.