A monthly performance comparison of green infrastructures enhancing urban outdoor thermal comfort

Among the problems caused by the increase of the urban heat island phenomenon, the worsening of the
outdoor thermal comfort at pedestrian level was addressed to improve urban resilience. Starting from the
analysis of a real urban area in Venice, Italy, the study was extended to different urban forms classified by
the Local Climate Zones (LCZs) method. The Physiological Equivalent Temperature (PET) calculated with
the ENVI-met code was used to evaluate outdoor thermal comfort. Different mitigation strategies were
compared for the whole summer period. For this purpose, a monthly assessment was performed using
the monthly mean day approach rather than the usual single days analysis. A new index (%DPET) was
proposed, indicating the percentage reduction in the discomfort rate in PET of the original scenario
achieved by mitigation measures. The results show that the largest PETs, corresponding to very hot
human thermal sensation, for the original scenario occur in the case of lowrise buildings. In this case,
green and cool roofs provide their best performances and the seasonal %DPETs reach 9.1% and 7.5%,
respectively. Green wall technology is the most effective in all urban forms studied with %DPET values
ranging from 28% to 115%, sometimes reaching the neutral comfort level.