Microclimatic effects of planted hydroponic structures in urban environment: measurements and simulations

The objectives of this effort was to study the effect of vertical (green wall) and horizontal (pergola) green structures on the microclimate conditions of the building surroundings and estimate the thermal perception and heat stress conditions near the two structures. The experimental data were used to validate the results simulated by the recent version (V4.0 preview III) of ENVI-met software which was used to simulate the effect of different design parameters of a pergola and a green façade on microclimate and heat stress conditions. Further aim is to use these results for better design of green structures. The microclimate measurements were carried out in real scale structures (hydroponic pergola and hydroponic green wall) at the Kostakii Campus of the Technological Education Institute of Epirus (Arta, Greece). The validation results showed a very good agreement between measured and simulated values of air temperature, with T_air,sim = 0.98 T_air,meas in the Empty atrium and T_air,sim = 0.99 T_air,meas in the Atrium with pergola, with a determination coefficient R ² of 0.98 and 0.93, respectively. The model was used to predict the effects of green structures on air temperature (T_air), relative humidity (RH), and mean radiant temperature (T_mrt). The output values of these parameters were used as input data in the RayMan pro (V 2.1) model for estimating the physiologically equivalent temperature (PET) of different case scenarios. The average daytime value of simulated air temperature in the atrium for the case without and with pergola during three different days was 29.2 and 28.9 °C while the corresponding measured values were 29.7 and 29.2 °C. The results showed that compared to the case with no pergola in the atrium, covering 100% the atrium area with a planted pergola reduced at the hottest part of the day T_mrt and PET values by 29.4 and 17.9 °C, respectively. Although the values of air temperature (measured and simulated) were not greatly affected by the presence of a green wall, the most important effect of green wall to the building wall is the reduction of solar radiation behind the green wall. This reduction leads to a significant reduction (about 8 °C) of building surface temperature behind the green wall and accordingly to a reduction of the energy load of the building.