Effect of urban green infrastructure on psychological and physiological responses under outdoor heat exposure: An experimental study

Urban residents are increasingly threatened by extreme heat exposure. While green infrastructure is widely recognized for its cooling and restorative benefits, empirical evidence is limited regarding its influence on psychological and physiological responses in real-world outdoor environments. In this backdrop, human subject experiment was conducted to investigates the effects of urban green infrastructure: green wall (GW) and green roof (GR) – under outdoor heat stress conditions, and measured Wet-Bulb Globe Temperature (WBGT), thermal perception, Profile of Mood States (POMS), heart rate (HR), and electroencephalogram (EEG) responses. Five spatial settings were tested: a bare wall (control), a GW with live plants, a GW with live plants (back-facing), a GW with artificial plants, and a GR with live plants. All green infrastructure settings significantly reduced WBGT compared to the control. Also, green settings were associated with improved thermal perception and mood states, with more pronounced effects observed under direct visual exposure to greenery. EEG data revealed decreased δ power and increased θ and β power across green settings, while α power was contingent upon the presence of visual exposure to greenery. These findings emphasize the potential of green infrastructure to enhance urban thermal comfort and mental well-being, particularly through visual interactions with greenery.