Utrecht Pilot Report

Mitigating heat stress through private greening and active community management In 2024 and 2025, the Municipality of Utrecht, the Province of Utrecht, and the Utrecht Nature and Environment Federation carried out two citizen science campaigns with the name Groene Buurt, Koele Buurt,(Green Neighbourhood, Cool Neighbourhood) to better understand heat stress in vulnerable neighbourhoods: 1. Heat Stress Campaign: 160 residents formed a community and measured temperature, humidity, and (dis)comfort in four green-poor neighbourhoods of Utrecht (Ondiep, Zuilen, Rivierenwijk, Kanaleneiland) during the summer months of 2024 and 2025. 2. Thermal Perceptions Campaign: research into thermal perceptions conducted via on-site surveys of previously identified “cool and hot spots” in summer 2025. An inclusive approach was adopted, actively engaging vulnerable groups, such as residents with limited language skills or financial resources, in data collection and in discussions on potential solutions. This ensured that diverse perspectives were represented throughout the process. Key insights: Neighbourhoods are, on average, 4–5 °C warmer than the Bilt monitoring station, especially at night. Greenery and shade demonstrably reduce heat stress; paved streets remain hotspots. Residents marked 239 hotspots and 41 cool spots; interviews link measurement data to perception. Data confirm KNMI models and offer new opportunities for analysing humidity and social factors. The use of the sensor and app was not yet optimal, which was frustrating for users. Participants remained engaged thanks to social cohesion. Impact and next steps: Residents are developing concrete greening and shading plans (pergolas, façade gardens, tree pits). Subsidy applications and creative projects are being prepared to share insights widely. In 2026, it will be explored whether the existing Groene Buurt, Koele Buurt community can be mobilized for other greening and cooling initiatives. Conclusion: The aggregated data from the citizen science project Groene Buurt, Koele Buurt, as part of Urban ReLeaf, offer valuable insights for research and urban planning. While individual-level data from the app and sensors are not yet fully suitable for use with vulnerable groups, the project’s community-building efforts have strengthened social cohesion and fostered a sense of agency in climate awareness and greening initiatives. These outcomes support municipal climate adaptation strategies and contribute to creating a fairer, cooler, and more resilient living environment.