Absolute environmental sustainability assessments guiding the building industry towards sustainable practices

With the increasing urgency to address the anthropogenic impacts on the Earth system, it is imperative to empower stakeholders in the building industry to take informed decisions. To fully understand the building sector’s current environmental impacts as well as mitigation potentials and risk of burden shifts, quantitative assessments are necessary. This thesis delves into the application of absolute environmental sustainability assessments (AESA) in the building industry, paving the path for aligning industry with the “safe operating space for humanity”.

The PhD thesis encompasses research rooted in three key scientific papers, each examining different scopes, from individual buildings, to building stocks in an area, to all new construction in Denmark. It addresses dynamic climate change budgets for individual buildings, mitigation potentials of construction products, quantification of mitigation strategies for building stocks, and how far technological advancements can take the Danish building sector towards complying with the planetary boundaries.

Article I introduces a framework for establishing dynamic GHG budgets for individual buildings that are aligned with the Paris Agreement, translating global emissions pathways to national and sector-specific climate budgets. It applies this framework to the Danish building sector, demonstrating how global GHG budgets can be translated to building GHG budgets using the metric kgCO₂/m². The budgets can guide building owners and industry professionals to set absolute targets and inform policymakers about the ambition level that is needed if current construction activity levels continue.

Article II focuses on the assessment of mitigation strategies for building stocks, relating them to GHG budgets that follow from different global GHG emission pathways and the threshold for climate change set by planetary boundaries. The study scrutinizes the efficiency of various mitigation strategies for building activities in a campus area and underlines the necessity of ambitious action, challenging the current operational energy consumption in the existing building stock and trends in the demand for new buildings. The study evaluates the environmental impact across 18 impact categories, and the mitigation strategies are examined both in terms of mitigation potentials and burdens shifts from climate change towards other impact categories. The paper illustrates how the quantification of environmental impacts and effects of different mitigation strategies provide decision makers such as local authorities, urban planners and portfolio owners with information needed to take informed decisions.

Article III combines prospective life cycle assessment (pLCA) and absolute environmental sustainability assessment (AESA) as tools to steer environmental strategies within the building sector. It identifies impactful material s in terms of mitigation potentials and uses a dynamic modelling until 2050 to evaluates the tradeoffs in material substitution, testing a shift towards biobased materials and a reduction in construction activity. The article highlights that relying on technological advancements alone is insufficient to achieve sustainable practices and thus calls for a rapid transformation in current consumption patterns. Furthermore, the study highlights potential over- and underestimation of future environmental impacts when not accounting for future changes in the background system of the built environment. The study thus encourages adjustment of current LCA methodologies, of particular relevance for the building sector, to ensure relevant assessments for long term strategic decision support.

This thesis contributes to the discourse on absolute environmental sustainability in the building industry by showcasing how these methods can be applied in a Danish context. The thesis offers examples of how quantitative decision support can be unfolded at different levels from individual buildings to the building sector to support different types of decision makers from industry professionals to policymakers.