Due to climate change, urban heat stress is becoming an increasing problem, affecting mostly vulnerable populations. Tenants of social housing are particularly vulnerable to the effects of extreme heat, due to inadequate social housing conditions and limited financial resources for cooling interventions. However, due to limited financial resources, housing corporations struggle to implement heat stress mitigation measures into their existing building stock. Therefore, this thesis examines how heat stress mitigation measures for the existing social housing stock can be both socially and financially viable. The formulated research question of this thesis is: What are the long-term costs and benefits of mitigating heat stress in the existing social housing stock?
To answer this research question, a mixed method approach was adopted, in which the first part of the research encompassed a literature review, followed by an empirical case study on Rotterdam. The findings of the research reveal that if indoor heat stress in social housing remains unaddressed, it poses significant risks to the health, energy and financial sectors. Health impacts, such as heat-related mortality and hospitalizations, emerged as the most severe impact, both in human and economic terms. The climate risk assessment indicated that under the high climate scenario, the risk of heat stress in Rotterdam rises significantly. Furthermore, the areas identified as most vulnerable to heat stress socially and (bio)physically are Delfshaven, the Oude Noorden, and the upper south of Rotterdam. In terms of mitigation strategies, the research concluded that passive measures such as shading and natural ventilation are the most effective way to reduce indoor heat stress. Lastly, the societal cost-benefit analysis demonstrated that, under both low and high climate scenarios, the benefits of mitigation outweigh the implementation costs. However, these benefits are unevenly distributed. While housing corporations bear the costs, the benefits accrue to the health, energy, and financial sector. This creates a split incentive that challenges implementation. In conclusion, reducing heat stress in social housing is both societally and economically beneficial. However, while the societal advantages are evident, practical feasibility requires stronger financial support.