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The operational energy use is responsible for an important share of the life cycle environmental impact of buildings. In the national LCA method for buildings in Belgium, as in most environmental impact assessments, operational energy use and associated impacts are kept unchanged throughout the 60-year service life of the building. The energy mix will however change over the building life cycle and this will influence the impact of the operational energy use. The overall aim of this paper is to analyse how long term temporal changes in the electricity mix in Belgium might influence the life cycle environmental impact of buildings using an attributional approach. This paper focuses on three aspects. First, it analyses future scenarios for the Belgian electricity mix as it is uncertain how it will change over time. Second, the environmental impact of these changes in the mix is evaluated using the Belgian life cycle impact assessment method for buildings considering a broad set of indicators. Finally, it is investigated how these changes in the electricity mix during the building service life can be included in the attributional life cycle assessment and how this influences the overall environmental impact of the operational phase. Within this study, three dynamic scenarios are defined and compared with the static approach, i.e. current electricity mix remains unchanged during the next 60 years. The analysis reveals differences in the building life cycle environmental impact of −29% and +34% compared to the current static approach, while differences in the life cycle carbon footprint range from −59% to +33%. This highlights the importance of considering changes in the electricity mix in LCA of buildings and in considering a broad range of environmental indicators instead of solely focussing on greenhouse gas emissions when making policy decisions. In general, a major challenge for the next decade seems to be phasing out nuclear power, without increasing the environmental impact of the electricity mix. [Display omitted] [ABSTRACT FROM AUTHOR]