The potential of facade greening in mitigating the effects of heatwaves in Central European cities

Abstract

This study investigates the potential of living walls in improving the climatic quality in the urban environment. To achieve this goal, numerical simulations using the urban microclimate modelling tool ENVI-met were conducted to analyse the distribution of air temperature, mean radiant temperature (MRT), relative humidity, and wind speed in a residential block in Stuttgart, Germany. The impact of the living wall on the interior air temperature was investigated as well. Before the simulations were conducted, the model was first validated against measured data collected in Weimar, Germany. The validation showed a fairly good agreement between the measured and simulated air temperature, MRT, relative humidity, and wind speed with an averaged respective mean absolute error (MAE) of 0.72 K, 2.67 K, 3.98%, and 0.30 m/s. The simulation of the residential area in Stuttgart indicated that facade greening has only a little impact on air temperature (−0.57 K). Yet, a reduced MRT by up to 3.04 K and a reduced interior air temperature by up to 3.8 K were observed. The living wall also had an impact on the relative humidity among the buildings, which was increased by a maximum of 5.07%. Only a marginal impact on airflow between buildings was observed when facade greening was implemented. Yet, air velocity directly in front of the foliage was reduced by an average of 0.25 m/s.