Greening guidelines for cooling European neighbourhoods with temperate climate

Abstract

Green infrastructure measures such as street tree planting and ground surface greening effectively mitigate urban heat. As heat stress intensifies, identifying effective spatial arrangements of these interventions becomes increasingly important. To provide actionable guidance for real-world projects, practical design and resource constraints must also be considered. However, studies that systematically balance cooling effectiveness with practical applicability remain limited. This study develops design guidelines on the size, amount, and spatial distribution of street trees and grass in urban neighbourhoods, focusing on applicability in urban design practice. Four neighbourhood typologies in temperate-climate European cities were used as case examples, for which multiple greening scenarios were generated. A research-through-design approach was adopted: focus group workshops with practitioners evaluated the scenarios in terms of visual experience, functionality, cost, and maintenance; then the refined designs were assessed using ENVI-met simulations. The refined scenarios reduced mean PET by 1.07–7.89 °C compared with the no-greening reference case, with the strongest reductions in wide-street typologies. However, greater green coverage did not necessarily lead to stronger cooling: in a narrow-street typology with diagonal street orientations, the tree-only scenario reduced mean PET by 1.79 °C, while the tree–grass scenario with higher tree and grass coverage reduced mean PET by 1.33 °C. For each typology, two recommended scenarios are identified: one maximising cooling capacity and one prioritising cooling efficiency under space and resource constraints. By translating thermally ranked scenarios into practitioner-refined greening guidelines, this study provides design support for neighbourhood-scale, morphology-specific heat mitigation through the strategic spatial arrangement of street trees and grass.