Effects of vertical greenery on mean radiant temperature in the tropical urban environment

Studies on vertical greenery generally focus on the measurement of air temperature, surface temperature and cooling load. There is a lack of information on how vertical greenery can influence outdoor thermal comfort. The objective of this study is to quantify the effects of mean radiant temperature (t_mrt ), as the first step towards determining the thermal quality of outdoor space due to installation of vertical greenery. 

The t_mrt of two green walls (Green Wall A and Green Wall B) was measured up to 2 m away at intervals of 0.5 m. Two datasets were obtained, one consisting of t_mrt , surface and air temperature collected from the two green walls and the second for just green wall A and the exposed concrete wall after Green Wall B was removed. t_mrt was measured using customised globe thermometers calibrated for local use. Data was analysed using a GIS, thus enabling convenient visual comparison between t_mrt profiles at different times. The diurnal t_mrt profile was altered significantly due to the installation of vertical greenery. When both green walls were present the peak t_mrt occurred at 15:00 h, but with more concrete exposed when one wall was removed, the peak occurred at 17:00 h and was 10.9–12.9◦ higher at 0.5 m away from the wall. Vertical greenery thus helped to reduce t_mrt both during the day and at night, to varying extents. The proposed methodology enables systematic quantification of the effects of vertical greenery on t_mrt.