Retrofit vs. replacement of multi-family houses – an energy, cost, and life cycle assessment perspective

Abstract A notable portion of greenhouse gas emissions of the built environment originates from the operation of the existing building stock, highlighting the importance of the “renovate or replace” dilemma. This study addresses the dilemma for a range of German multi-family houses (MFHs) by considering the trade-offs among energy efficiency, cumulative (i.e., embodied and operational) CO 2 -eq emissions, and costs. First, five MFHs from different construction periods were selected, modeled, and assigned to typical construction archetypes. Then, the energy consumption, cumulative CO 2 -eq emissions, and costs for various renovation and replacement scenarios, considering different energy technologies, were evaluated over the next twenty-five years. The obtained results suggest that replacement measures have the highest potential for energy savings, while full retrofit measures lead to the most significant decrease in cumulative CO 2 -eq emissions. Due to its considerable reduction in energy consumption, greater climate benefits, and relatively low costs, full retrofit comprising the installation of a heat pump and photovoltaic panels may be the optimal solution for MFHs in Germany.