Deep building energy retrofit can lead to a significant reduction of energy demand and environmental impacts, but national retrofit rates in Europe are currently below 1%/a. This thesis therefore aims for a better understanding of the cost-effectiveness of energy retrofit measures, considering technological, geospatial, stakeholder and temporal dimensions. For this, a comprehensive modelling framework for the Swiss residential building stock is developed, comprised of a statistical analysis of energy certificates, a physics-based bottom-up model, dynamic calculation of lifecycle costs and a scenario analysis of possible retrofit pathways. The results confirm: 1) the urgent need for substantial energy demand and impact reduction, 2) the high technical saving potential, 3) moderate to high current economic energy and GHG saving potential 4) high dynamic technical and moderate economic energy and GHG saving potential. This thesis ultimately demonstrates that early and deep energy retrofit can contribute both to the technical and economic potential.