Optimizing the combination of active and passive building components in refurbishment projects to allow for net-zero emission architecture

Buildings have always been constructed as a combination of active and passive building components, which help balancing fluctuating exterior conditions. Although this combination first and foremost serves to guarantee thermal comfort, it also reflects cultural aspects and the state of technological knowledge. Allochthonous architecture replaced local autochthonous architecture worldwide due the availability of cheap fossil fuels. At the same time, new technologies fostered the demand for higher comfort in buildings. However, the operation of this type of buildings requires inacceptable quantities of non-renewable resources and generates intolerable volumes of green house gas emission (GHGs). It is scientific consensus today that GHGs from buildings need to be reduced. Still, there exists an uncertainty about how to match the expectation regarding the aesthetics of architecture with the challenge of radically reducing the building related GHGs. This thesis assesses four methods (Reduction-, Combination-, Substitution- and Combination Method) to reduce the equivalent annual global warming potential (GWPe,a) of existing buildings. Based on a simplified model of a residential building, the methods are assessed with case studies regarding their efficiencies in terms of the GWPe,a reduction and of equivalent annual cost. The consequences regarding the architectural design and aesthetics of buildings are highlighted with built examples. One important finding is that the established architectural methods regarding sustainable design, like optimizing the compactness and orientation of buildings or optimizing the percentage of windows, are of less importance than active strategies of improving the heating and cooling system or substituting the purchased power. Finally, the optimization of the different methods shows that several combinations of active and passive building components exist, which result in the same or similar strong reductions of the GWPe,a. Consequently, the idea of an irreconcilability of architectonic quality and refurbishing towards net-zero emission is invalid, as several solutions exists that allow for sufficient architectural alternatives.