The impact of evolving mix on building's life cycle environmental impacts under climate change: insights from a London office case study.

Purpose: The main aim of this study is to identify how evolutions in the electricity mix and climate change affect the LCA results of buildings regarding the multitude of environmental impacts. This is of critical importance now, and one that is likely to receive growing interest in the future. Firstly, because carbon might become a secondary environmental impact to mitigate as economies achieve decarbonisation milestones, and secondly, due to concerns around the trade-offs between the environmental impacts. Methods: This study evaluates the lifecycle environmental impacts of a case study office building in London by considering climate change in the UK (using CIBSE weather files) and electricity mix evolution in the UK (using National Grid ESO data), EU (using EU commission data) and China that influence operational and embodied modules of LCA. Electrification of transport is also considered, reflecting the forementioned electricity mixes. A dynamic LCA approach was followed in which the inventory was modified to reflect future electricity mixes. The influence of climate evolution was considered through dynamic thermal simulations according to London's future climatic projections provided by CIBSE's weather files that were then translated into lifecycle environmental impacts through the modified inventory. Results and discussion: Results of applying a dynamic approach in LCA show that there are several co-benefits of grid decarbonisation when it comes to the building's environmental impacts. However, ecotoxicity and land occupation might come to light. Climate change led to minor reductions in the operational electricity needs, indicating that no significant savings are to be expected in the case of actively cooled buildings without free ventilative cooling. Evolving electricity mixes do not significantly reduce material embodied impacts for this case study, showing that the reduction of lifecycle impacts cannot rely only on future electricity mix evolutions. The electrification of transport was found to have an adverse effect on the building's embodied ionising radiation impact, highlighting the importance of sourcing materials locally to avoid long transportation distances. A new type of performance gap is proposed for the building's lifecycle environmental impacts. This can be defined as 'the difference between the predicted and the actual environmental impact resulting from the mismatch between the actual case and the life cycle inventory'. Conclusions: Future research is needed to investigate how sensitive results are to other assumptions and how improvements in material manufacturing affect the obtained results.