Switzerland faces increasing pressure to address climate change, with reducing CO2 emissions being a top priority. The building sector plays a significant role in this challenge, contributing approximately to 22% of national emissions. At the local scale, the impact is even greater: in Lausanne, buildings account for 58% of territorial emissions, making them a key lever for achieving climate targets. In response, the city of Lausanne has set the ambitious goal of renovating 100% of its building stock by 2050, as part of its Climate Plan. Reaching this target requires a deeper understanding of the drivers, constraints, and dynamics of energy renovation—a gap this study seeks to address.
The research employs a scenario planning approach, supported by both quantitative data analysis and qualitative expert interviews. To inform scenario development, a comprehensive assessment of the current socio-technical context of Lausanne’s building stock was conducted. This included analysis of energy needs, ownership structures, legal frameworks, and existing measures, helping to identify the key variables influencing renovation trajectories. Based on these insights, eight scenarios were constructed along three main dimensions—political, economic, and social—plus a fourth dimension evaluating the impact of additional public action. From these, three representative scenarios were selected for deeper analysis. A sensitivity analysis was also performed, focusing on critical factors such as renovation costs, subsidy levels, and rent increase limits.
The findings reveal that under favourable conditions, energy needs could be reduced by up to 60%, with nearly the entire building stock renovated. In contrast, under unfavourable conditions, reductions could be limited to 20%, with only 60% of buildings renovated—highlighting the importance of public intervention. Targeted additional measures (e.g. DDP (Distinct and Permanent Right of Surface) rights, soft power, building raisings, lower interest rates, additional subsidies) could double the energy savings in these less favourable scenarios. Overall, the new cantonal energy law will serve as a strong driver of renovation, as it applies to nearly half of Lausanne’s buildings. For the remaining stock, renovations are expected to occur primarily when they are financially profitable or thanks to the additional measures stated just above.
The study also identifies that in challenging scenarios, up to 35% of buildings—almost 4,000 in total—require additional public action to be renovated. These are mainly owned by co-owners, private individuals, and large enterprises, with the highest surface renovation needs concentrated in the city center, and the largest number of buildings in the north east districts. It is argued that both core measures—such as financial support mechanisms that make renovations feasible (e.g., additional subsidies)—and supporting measures—such as renovation audits that help inform and guide owners—ar
