Integrating Building Characteristics and Access to Climate Shelters to Assess Urban Heat Vulnerability

• Replicable open data methodology to assess building adaptive capacity to extreme heat • Cross-ventilation potential as a key factor for climate adaptation • Priority areas are identified to strengthen passive climate resilience strategies • Most of Barcelona’s housing units show high levels of adaptive capacity As extreme heat events intensify and the share of fragile population in cities grows, addressing climate vulnerability becomes increasingly pressing. Existing vulnerability assessments mainly rely on socio-economic indicators, while public authorities have responded by deploying climate-shelter networks. Yet, current approaches overlook the built-environment by not considering residence’s indoor climatic conditions, the proximity of shelters to vulnerable housing, or the typologies of those shelters. This study fills these gaps by developing a novel index, based on cross-ventilation potential of housing buildings, to target the adaptive capacity dimension of heat-vulnerability. We implement it in Barcelona and spatially align it with accessibility to climate shelters, using a replicable GIS-based open data framework. Results reveal marked spatial disparities: dense historic districts show low ventilation potential, while central Eixample and areas near Collserola exhibit greater adaptive capacity. Post-war neighbourhoods lack passive-cooling opportunities. Cross-referencing with shelters shows that around 30% of homes cannot rely on passive cooling strategies nor nearby public facilities to withstand extreme heat episodes. These insights support targeted rehabilitation, identification of thermally vulnerable housing clusters, and optimisation of climate-shelter provision for cities facing escalating heat stress.