Energy-Saving Strategies for Enhancing Outdoor and Semi-Outdoor Thermal Comfort in Smart Cities: A Systematic Review

Thermal comfort in urban environments is increasingly being addressed through smart, energy-efficient strategies, especially as cities adapt to rising temperatures and sustainability mandates. This study presents a systematic review of recent research on energy-saving methods for improving outdoor and semi-outdoor thermal comfort in smart cities. Articles were sourced from Scopus and Web of Science (2020–2025), and analyzed based on applied methods, effectiveness, and geographic distribution.
The reviewed literature highlights five main categories of strategies: (1) passive interventions (e.g., vegetation, phase change materials, reflective coatings), (2) smart materials (e.g., thermochromic windows and bioinspired textiles), (3) AI-driven HVAC and thermal control systems, (4) sensor-based human-centric feedback loops, and (5) integrated energy management systems (EMS) including residential energy hubs. China and the USA lead in research output, with significant contributions from Spain, India, and the Netherlands.
Reported effectiveness varies by method and context: passive solutions reduced MRT by 2–5°C and surface temperatures by up to 20°C; AI-based controls achieved HVAC energy savings of 20–30%; and thermochromic coatings lowered cooling demands by 10–25%. Despite technological advances, relatively few studies incorporate human thermal perception data or prioritize equity in thermal comfort distribution.
This review identifies key innovation trends and proposes a classification framework for energy-efficient thermal strategies in smart urban contexts. Future research should emphasize user-centered metrics, interdisciplinary integration, and implementation across varying climate zones, especially in vulnerable regions