As climate change accelerates, extreme heat events will intensify, threatening vulnerable populations experiencing dangerous heat outdoors. Active radiant cooling has recently emerged as a promising strategy for outdoor thermal comfort, at it offers cooling at a distance without the inefficiency of conditioning unconfined air. However, for radiant cooling structures to be effective, the overwhelming majority of their internal surfaces must be actively cooled, typically with visibly opaque panels, raising practicality and safety concerns. Here, we demonstrate that thermal comfort can be achieved in an outdoor cooling structure that lightly uses radiant cooling and amplifies this cooling effect using visibly transparent, infrared-reflective surfaces. This approach enables visibly open cooling structures that will be accepted by a wide range of communities. We first derive an analytical model that relates the mean radiant temperature to the proportion of cold and reflective surfaces in a structure. We then experimentally demonstrate such a structure, with human subject testing revealing a substantial enhancement in thermal comfort as experienced by occupants. Our results highlight how next-generation radiant cooling structures can use fewer actively cooled surfaces without compromising on cooling effectiveness. This is a practical approach to enabling thermal comfort outdoors in extreme heat conditions.

Mackensie Yore (VA Los Angeles and UCLA National Clinician Scholars Program, VA Greater Los Angeles Healthcare System HSR&D Center of Innovation, Department of Emergency Medicine, West Los Angeles VA Medical Center, VA Greater Los Angeles Healthcare System, Department of Emergency Medicine, UCLA David Geffen School of Medicine), Xin Huang (Department of Materials Science and Engineering, University of California, Los Angeles), V. Kelly Turner (Urban Planning Department, Luskin School of Public Affairs), Walker Wells (Urban Planning Department, Luskin School of Public Affairs), Kirsten Schwarz (Urban Planning Department, Luskin School of Public Affairs, Department of Environmental Health Sciences, Fielding School of Public Health), David P. Eisenman (David Geffen School of Medicine at UCLA, Department of Medicine), Aaswath P. Raman (Department of Materials Science and Engineering, University of California, Los Angeles)

Abraham, D.E., Yang, R., Mandal, J. et al. Efficient outdoor thermal comfort via radiant cooling and infrared-reflective walls. Nat Sustain 8, 642–650 (2025). https://doi.org/10.1038/s41893-025-01558-0