Defining dynamic science-based climate change budgets for countries and absolute sustainable building targets

Given the current climate crisis countries and sectors need to set targets and address reduction potentials for their greenhouse gas (GHG) emissions. The current use of bottom-up benchmarks for the building sector enables relative sustainability comparisons. However, we must start relating the environmental performance of buildings to science-based targets. Therefore, this study introduces a procedure for downscaling the global GHG budget to country-specific top-down targets for embodied impacts in buildings. Earlier studies have shown how sharing principles can be applied to calculate absolute limit values for buildings, however, this study will show how a dynamic GHG budget in line with the Paris Agreement target of limiting temperature increases to 1.5 °C can be applied. The global GHG budget is then scaled down to national level and further down to the building sector, and finally to the construction of a new building. The downscaling method tested four combinations of the sharing principles applying equal per capita, ability to pay, utilitarianism, and acquired rights. The proposed procedure was applied to the Danish building sector, revealing that for the four sharing principles, the national legislation exceeds the average target values by up to 220% in 2023. By relating global climate targets to national targets for buildings, the results have the potential to guide decision-makers such as building designers in setting relevant science-based targets as well as policymakers in setting the necessary ambition level for national strategies related to the transformation of the building sector into sustainable practices.