Vertical green systems for buildings climate control

The phenomenon of urban warming, known as urban heat island, negatively influences outdoor comfort conditions and pollutants concentration and as well increases the environmental impact due to the energy demand for air conditioning. Urban warming can be attenuated by reducing the solar heat gain that increases building’s temperature during the hot season. Solar heat can be mainly reduced by increasing the insulation between the exterior and interior of the building, as well as by shading the building surface from direct sun exposure. A sustainable technology for improving the energy efficiency of buildings is the use of green roofs and green walls that: allow the physical shading of the building and promote evapotranspiration in summer; increase the thermal insulation in winter. An experimental test was carried out at the University of Bari (Italy, 41 ° 05 'N, 16 ° 53 'E). Three prototypes of building vertical wall, made with perforated bricks, were designed: two vertical walls were covered with plants (one with Pandorea jasminoides variegated, the second with Rhyncospermum jasminoides) while the third wall was kept uncovered and was used as control. A system composed by a data logger and sensors was used to measure and record the following parameters: temperature of the wall surface under solar radiation and of the surface on the other side of the wall, solar radiation falling on the wall, external air temperature and wind speed. During summer 2014 the diurnal temperatures of the control surface exposed to the solar radiation were higher by about 4 °C compared to the temperatures recorded on both the vertical walls covered with Rhyncospermum jasminoides and Pandorea jasminoides variegated. The thermal wave propagated with a phase shift of about 2 hours and half.