Planning and building within planetary boundaries. From the singular target of climate neutrality towards a holistic climate and resource-saving building design - a case study.

Abstract The German government has committed to GHG neutrality by 2045. This implies the designation of a physical quantity whose zero line ensures the achievement of the goals of the Paris Agreement. To date, a binding definition of terms with specifications on the assessment scale and method, system boundaries and on acceptable compensation measures is lacking. Since every construction process creates an ecological footprint, ‘GHG-neutral buildings’ can only be understood as a calculation model for the longer-term compensation of the climate and environmental damage that is currently being caused. A reduction to GHG-emissions thus fails to achieve the goal of building within planetary boundaries. Within the building sector, the German Climate Protection Act only takes into account energy consumption during the operational phase, leaving out emissions that occur in other life cycle stages i.e. sectors. Thus, no incentives are created to exploit a wider cross-sectoral climate and environmental protection potential of the entire buildings’ lifecycles. Existing definitions of the concept of ‘climate and GHG-neutrality’ are analysed in general and specifically in relation to buildings. Research criteria are calculation bases and life cycle-related system boundaries. Based on a built case study, life cycle assessment (LCA) is used to quantify the ‘delta’ resulting from divergent definitions in terms of GHG-emissions. This paper will quantify emissions according to divergent definitions of climate- and GHG-neutrality for a new construction scenario and also for a renovation scenario, as well as two different building material scenarios. Also, the paper will derive emission reduction potentials of sufficiency measures by applying LCA already in an early design process. To outline the role of buildings in decarbonizing the built environment, the entire life cycle is considered, including those modules that are currently outside the standard. Additional indicators (e.g. consumption of fresh water or total material input) are discussed regarding a possible shift in the ecological footprint and the building’s adherence to planetary boundaries.