Too little too late: An empirical study of renovation of building elements

Building retrofits hold considerable potentials for reducing energy consumption. A full exploitation of such potentials requires timely renovations and sufficient investment in the existing building stock, in accordance with economic considerations. Using data from a household survey in Switzerland and focusing on replacement patterns for heating systems, windows, façades and roofs, we analyze the owners' renovation behavior and its possible deviations from norm-based recommendations. As opposed to most previous studies that assume a linear age effect, we model the renovation probability as a conditional hazard rate with a more flexible representation of age effects. We compare the renovation patterns identified by the survival analysis with the service lives determined by building norms. We find significant deviations between the two, suggesting sub-optimal replacement but a mitigated picture of renovation delays as compared to norm-based values. While renovation of heating systems and windows represent no systematic delay, façades and roofs show a strong tendency for belated or little renovation. In particular, the results point to a considerable fraction of owners refraining from façade and roof retrofits, far beyond their technical service lives. We also identify a number of determinants for replacement timing, in view of energy policies aiming at the promotion of energy-saving renovations.