Per capita climate impacts: densification fails without floor space sufficiency

Densification is a global urban policy goal. However, its climate effectiveness is limited due to a focus on technical efficiency, overlooking socio-demographic occupancy shifts. This study bridges Life Cycle Assessment (LCA) based modeling and building-level occupancy data to quantify per capita climate impacts of residential redevelopment through building replacement (demolition and reconstruction) relative to refurbishment, analyzing 4000+ replacement projects in Swiss cities. Crucially, 14% of multi-family replacements fail to increase the number of people housed, as gains in total floor space are offset by rising per capita floor space. These projects lock in high embodied carbon for decades. In addition to material choice, climate impacts are highly dependent on institutional and regulatory contexts. Specifically, housing cooperatives successfully curb buildings’ per capita floor space by enforcing occupancy rules, such as limiting the number of rooms per person. For planning and policy, our results imply that densification does not reduce climate impacts without floor space sufficiency. Policy relevance In cities worldwide, densification is increasingly implemented by building replacement. Our findings suggest the following policy levers to reduce climate impacts of densification: (i) planning authorities should discourage replacements with low replacement ratio (small relative increase in floor space) since these often fail to house more people, (ii) cities should integrate a per capita perspective into zoning and planning processes, and (iii) prioritizing non-profit housing with occupancy rules in land-lease and up-zoning can effectively curb dynamics of increasing per capita floor space.