Prioritizing urban heat adaptation infrastructure based on multiple outcomes: Comfort, health, and energy

Journal Article · Mon May 05 00:00:00 EDT 2025 · Proceedings of the National Academy of Sciences of the United States of America

DOI:https://doi.org/10.1073/pnas.2411144122· OSTI ID:2566875

Jiang, Timothy ^[1]; Krayenhoff, E. Scott ^[2]; Martilli, Alberto ^[3]; Nazarian, Negin ^[4]; Stone, Brian ^[5]; Voogt, James A. ^[6]

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1. Univ. of Guelph, ON (Canada); Pacific Northwest National Laboratory (PNNL), Richland, WA (United States)
2. Univ. of Guelph, ON (Canada)
3. Centre for Energy, Environmental and Technological Research, Madrid (Spain)
4. Univ. of New South Wales, Sydney, NSW (Australia)
5. Georgia Institute of Technology, Atlanta, GA (United States)
6. Western University, London, ON (Canada)

Globally, cities face increasing extreme heat, impacting comfort, health, and energy consumption. Infrastructure-based heat adaptation strategies can improve these outcomes, but each strategy has a unique mix of benefits and drawbacks. Here, we apply an urbanized meteorological model (WRF) with the newly integrated multilayer BEP-Tree street tree model to dynamically downscale Earth System Model projections and a 3-D microclimate model (TUF-Pedestrian) to simulate the street-scale radiation environment impacting pedestrians. We evaluate the performance of five heat adaptation strategies (street trees, cool roofs, green roofs, rooftop photovoltaics (PV), and reflective pavements) during extreme heat events in three cities with contrasting background climates (Toronto, Phoenix, and Miami), under contemporary and end-of-century projected climates, based on three metrics: outdoor heat stress, air conditioning (AC) energy use, and ventilation of vehicular air pollution. No single adaptation strategy improves all three outcomes. While street trees inhibit ventilation, they reduce outdoor heat stress four times more effectively than the next best strategy via shade provision, fully offsetting heat stress increases under a high-emissions end-of-century climate scenario in all cities studied. Cool roofs and green roofs moderately reduce heat stress and energy use. Alternatively, rooftop PV with energy storage can generate sufficient power for space cooling but have marginal effects on heat stress. Reflective pavements are the least effective across metrics. Where the ventilation of street-level emissions is of less concern, our results clearly support the combination of street trees and rooftop PV as a highly complementary and effective means of adaptive mitigation across different climates and neighborhood densities.

• Research Organization: Pacific Northwest National Laboratory (PNNL), Richland, WA (United States)
• Sponsoring Organization: USDOE
• Grant/Contract Number: AC05-76RL01830
• OSTI ID: 2566875
• Report Number(s): PNNL-SA--199341
• Journal Information: Proceedings of the National Academy of Sciences of the United States of America, Journal Name: Proceedings of the National Academy of Sciences of the United States of America Journal Issue: 19 Vol. 122; ISSN 0027-8424
• Publisher: National Academy of Sciences
• Country of Publication: United States
• Language: English

Related Subjects

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATION
air pollutant dispersion
extreme heat events
outdoor thermal comfort
space cooling energy use
urban heat mitigation