Green Façade to Improve Building Energy Performance in Summer and Winter

Greenery systems are passive technologies which allow increasing buildings thermal control making them less energy intensive. Among greenery systems for buildings, green façades seem to be a particular feasible solution. An experimental test was carried out at the University of Bari, under Mediterranean climate conditions. An evergreen double skin green façade was tested together with an unvegetated wall to grasp their different energy behavior. The experiment was conducted to study both the summer and winter functioning. Experimental data were used to compare microclimatic conditions characterizing the covered and the bare wall and to analyze the thermal energy transfer at the two walls. The green façade provided benefits during both summer and winter. In summer, the main positive effects concern the cooling of the wall surface and of the nearby air. Sensible reduction of the energy input, thanks to solar shading and plant evapotranspiration was recorded too. In winter, warming of the wall surface and nearby air and lower air velocity near the wall were the most relevant effects. The reduction of radiative and convective losses, thanks to the thermal and wind barrier role played by vegetation, provided further advantages. The improved thermal performance of the building achieved through the green façade positively affects the building’s energy requirements for cooling and heating. The findings of this research aid in increasing the knowledge on the performance of green façades in both warm and cold periods and the specific benefits provided.