Assessing biodiversity impacts of buildings: an evaluation of building elements and limitations in current assessment methods

Abstract Purpose This study evaluated the life cycle biodiversity impact of building exterior walls. While climate change is well-studied and addressed in the construction sector, its impact on nature and biodiversity remains underexplored. The aim of this article is to assess the consistency of different life cycle impact assessment (LCIA) methods and evaluate the biodiversity impact of various exterior wall systems that integrate conventional to biobased material. Method Using the life cycle assessment (LCA) method and the Ecoinvent database, we analysed seven exterior wall systems adhering to Danish building regulations of 2018. Impacts were assessed by the LCIA methods ReCiPe 2016, LC-IMPACT, and EN 15,804 + A2, and Environmental Product Declarations (EPDs) impact data for exterior wall construction products. Product-specific midpoint categories were converted to biodiversity impacts by using unit conversion factors from ReCiPe 2016. Land use in EN 15,804 + A2 was reconciled with other LCIA methods using linear regression. The examined wall types include steel, concrete, timber, cross-laminated timber, and products incorporating hemp and straw. Results The biodiversity rank of the seven wall systems were consistent across LCIA methods, with minor variations. The midpoint contributions appeared to vary more across methods, while the most considerable pressures generally were identified as ecotoxicity, terrestrial acidification, land use, and climate change. Gaps in EPD midpoint categories were detected, including land use indicator incompatibility and exclusions of marine and terrestrial ecotoxicity categories. Conclusions Consistent biodiversity rankings suggest that the LCIA methods are useful for decision‑making. However, variations in midpoint contributions may affect the prioritisation of mitigation efforts. It is not possible to conclude whether conventional or more biobased building elements have the least biodiversity impact because results fluctuate depending on the structural system. Aggregated land use factors in LCIA methods, particularly ReCiPe 2016, require refinement for forestry, metal and mineral extraction. Therefore, standardisation and legislative frameworks for LCA practices in the built environment should address and include the missing and incompatible midpoint categories.