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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.

It is important to manage the environment inside an horticultural greenhouse in order to guarantee suitable growing condition for the crop, safety condition for the workers and energy savings. Microclimate is influenced by climatic parameters, such as solar radiation, air temperature, relative humidity, and wind speed. Evaporative systems are generally used in warm regions for commercial greenhouse cooling, however such systems require large quantity of water that is often a scarce natural resource in Mediterranean areas. Solar absorption systems can be applied for greenhouse cooling in regions with high values of solar irradiation as alternative to evaporative systems by exploiting renewable energy sources. The solar cooling system could provide significant energy-saving opportunities for cooling greenhouses in hot climates allowing the reduction of electricity and water consumption by exploiting the contemporaneity between the cooling requirements and the solar energy availability. The paper presents the technical considerations on the application of a solar absorption cooling system to a greenhouse in the Mediterranean climatic region. The aim of the research was to define the solar collector surface related to the greenhouse cultivated area and the potential of the system in terms of cooling capacity and energy consuption. The simulation study was realized based on the experimental data collected at the experimental centre of the University of Bari, Southern Italy, in order to control the air temperature of a greenhouse covered with plastic film; the greenhouse was characterized by a surface of 300 m2. The cooling system was designed by adopting suitable technologies of energy saving, in order to reduce cooling energy needs. The designed system consists of an absorption chiller having a cooling capacity of 18 kW fed by 50 m2 of evacuated-tube solar collectors coupled to a new distribution system which provides the cooling power only for the air volume surrounding the crop and not for the whole greenhouse.

Nowadays the growth of the cities increased built and paved areas, energy use and heat generation. The phenomenon of urban warming, called urban heat island, influences nega-tively outdoor comfort conditions, pollutants concentration, energy demand for air condition-ing, as well as increases environmental impact due to the demand of energy generation. In-door air temperature depends on a combination of several different parameters related to the climate of the region, the building itself and its use. The main parameters influencing the mi-croclimate are: external air temperature and relative humidity, incident solar radiation, long wave radiation exchange between the structure and its surroundings, incidence and speed of the wind, air exchanges, physical and thermal properties of the building’s envelope materials, design variables such as building dimensions and orientation, presence of artificial light, and electrical equipment. In the Mediterranean region the main problem is to control the solar heat gain that increases building’s temperature during the hot season. Solar heat is trans-ferred to the internal air through the envelope by the heat transfer mechanisms as conduc-tion, convection and radiation. Solar heat can be reduced by increasing the insulation be-tween the exterior and interior of the building, shading the building surface from direct sun exposure, by using an adequate building’s envelope materials or by using green roofs and walls. The use of green roofs and walls can contribute to mitigate the phenomenon of heat island, the emissions of greenhouse gases, and the storm water runoff affecting human thermal comfort, air quality and energy use of the buildings. Aim of this paper is to describe the benefits, the design requirements and plants, and the heat transfer mechanism of green roofs and walls. Green roofs and green vertical systems can be used as passive energy sav-ings systems because they intercept solar radiation by the vegetation, provide thermal insu-lation by the vegetation and substrate, occur evaporative cooling by evapotranspiration from the plants and the substrate, and influence the effect of the wind on the building.