Life cycle-based parametric optimization of buildings towards climate neutrality and its implications for environmental protection

The climate crisis represents the greatest challenge to be solved by the current generation, according to the European Union. In relation to this, the building sector plays a crucial role since it is responsible for around 37% of the global CO2 emissions. To meet the internationally and nationally defined targets for climate neutrality, different strategies such as changing the energy systems or increasing energy efficiency are applied to reduce the CO2 emissions during the use phase of buildings. However, the current strategy has major deficits since essential parts of a building's life cycle (e.g. embedded emissions of the building construction) are neglected. In addition to climate protection, environmental protection is another global and national goal which is neglected by only focusing on the CO2 emissions. Since ecosystems provide vital ecosystem services for the survival of present and future generations, environmental protection is crucial to be considered. To show the effects of these current, limited approaches, this study displays and compares different parametric optimization strategies, such as focus on the use stage and focus on the whole life cycle of buildings, using thermal building simulations. To analyze the different approaches, the assessment boundaries are extended to the whole life cycle of buildings (product, use, refurbishment, and end-of-life) and to further environmental indicators (global warming/acidification/eutrophication potential). The results show that reducing the global warming potential (GWP) (unit: CO2-eq.) not necessarily implies a reduction regarding the acidification potential (AP) and eutrophication potential (EP). In fact, in some cases, the AP and EP are higher after a CO2-eq. focused optimization process. As a result, to plan and implement buildings and cities in a climate and ecological friendly manner, the current horizon of consideration must be expanded, and a multi-criteria optimization approach needs to be implemented as demonstrated.