Energy efficient renovation in a life cycle perspective : A case study of a Swedish multifamily-building

Abstract: Energy use in the European Union is increasing. At the same time, it is estimated that by the year 2050 most of the EU population will be living in currently existing buildings. Some of these buildings are or will be in need of renovation, and they have identified a target to reduce overall energy use. The urgency of climate change also makes it highly relevant and important to improve buildings resource and energy efficiency. This thesis aims to explain how different proposed energy efficient renovation strategies affect the energy use at different system levels, the potential environmental impacts of these alternatives, how they are connected to economic impacts and the implications of using a commercial LCA software to answer these questions from a research perspective.In order to answer the questions above, the effect of different renovation strategies were studied by combining building energy simulations, energy system simulations, a building environmental assessment tool, life cycle assessment and life cycle cost calculations. These tools are used in order to provide an overview of how the different renovation strategies affect the production of district heating, greenhouse gas (GHG) emissions and the environmental and economic performance of the building.The results show that the selected renovation strategies reduce energy use by decreasing transmission losses, while reducing the total amount of purchased energy by using solar energy or by changing energy carriers. These different approaches have the potential to reduce the environmental impact, mainly by reducing global warming potential, acidification potential and eutrophication potential and to some extent abiotic depletion potential. However, when changing energy carriers there is a burden shift to radioactive waste disposed. When the economic aspects are analyzed, it is shown that there is no simple correlation between financial and environmental impacts.To analyze a building from a life cycle perspective can help to identify the advantages and disadvantages of energy efficient renovation from the building owner’s perspective as well as from a societal perspective. Applying a life cycle perspective is therefore important for building owners, building companies and practitioners as well for policy makers to avoid suboptimisation.