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The Urban Heat Island (UHI) phenomenon induces harmful outdoor comfort conditions, an increase in pollutants concentration, an excessive energy consumption related to the greater use of air conditioning systems and a raise of the frequency and magnitude of electricity demand peaks. In the Mediterranean area the urban warming and the solar heat gain in buildings need to be controlled in a sustainable way for keeping the indoor temperature at comfortable values. Green roofs and green walls can mitigate the heat events related to UHI, lower the indoor temperatures, cut energy loads on buildings, enhance human thermal comfort conditions and increase the buildings thermal insulation in winter. Experimental tests were carried out at the University of Bari (Italy) starting from summer 2014, aiming to analyze the influences of different climbing plants, as main components of green systems, applied on building walls. Three vertical walls, made of perforated bricks, were built. They were equipped with a sealed structure, on their backside, in order to realize prototypes of buildings in scale. The first wall was covered with Pandorea jasminoides variegated, the second with Rhyncospermum jasminoides, the third wall was kept uncovered and used as control. Several climatic parameters concerning the walls and the ambient conditions were collected during the experimental test by means of a data logger and sensors. High defi nition infra-red images for each wall were recorded using a Thermal Imaging Camera for analyzing the surface temperature of the plants and of the walls. The daylight temperatures observed on the walls protected with plants during warm days were lower than the respective temperatures of the control wall up to 5 °C; the nighttime temperatures observed during cold days were higher than the respective temperatures of the control wall up to 3°C.

The Urban Heat Island (UHI) effect induces an excessive use of building cooling systems, increasing the energy consumption, airborne pollution concentration and greenhouse gas emissions into the atmosphere. The Green Walls can be used as passive energy savings systems for controlling the solar heat gain for the buildings in summer and for increasing their thermal insulation in winter, contributing to the UHI effect mitigation. Experimental tests were carried out at the University of Bari (Italy), from August 2014 to February 2015, aimed to analyze the contribution of green walls with two different plant species (Pandorea jasminoides variegated and Rhyncospermum jasminoides) to the building thermal performance. Three prototypes of building vertical wall were built; two walls were covered with plants and the third was kept uncovered for control. The collected data analysis pointed out that in warm days the maximum daylight temperatures observed on the external surface of the walls covered with plants were lower up to 4 °C than the respective temperatures measured on the control wall and during the nighttime of cold days the minimum temperatures measured on the external surface of the walls covered with plants were higher up to 2°C than the ones of the control wall.