Quantifying outdoor cooling effects of vertical greening system on mean radiant temperature

Abstract

Energy flux of Vertical Greening System (VGS) is crucial for understanding of heat exchange processes by optimizing the cooling performance in outdoor thermal comfort, thereby mitigating heat stress through the transpiration. To understand the potential cooling effect of VGS, we quantify the Mean Radiant Temperature (MRT) of VGS by analyzing radiation flux and evaluating cooling efficiency, defined as the ratio of the cooling effect provided by the VGS to the energy input necessary to achieve that effect to quantify the effectiveness of VGS. The VGS showed a decrease in net radiation by 120 W/ m2, resulting in a decline in MRT by 3.02 °C compared to the wall. Furthermore, we found that the cooling efficiency of transpiration in VGS was 7.38 times more effective than evaporation from soil without plants. These findings suggest that VGS has the potential to significantly reduce heat stress and serve as an efficient strategy in urban areas.

Keywords

• Outdoor thermal comfort
• Vertical greenery
• Cooling efficiency
• Radiation flux
• Transpiration