Green control of microclimate in buildings

In the Mediterranean area the solar heat gain in buildings needs to be controlled during the warm seasons in order to keep the internal temperature at comfortable levels and to mitigate the phenomenon of urban warming, known as Urban Heat Island. This phenomenon contributes to increase the outdoor pollutants concentration and the energy demand for air conditioning. Indoor microclimate conditions depend on several parameters related mainly to the building destination, envelope materials and orientation, its technological equipment, and to the specific region climate. The use of green shading can induce energy savings also in winter, by reducing heat losses from the external surface during mainly the night. An experimental study was carried out at the University of Bari (Italy, 41° 05 ‘N, 16° 53 ‘E) from June 2014 to April 2015 with the aim of investigating the effective influences of this green passive system on a building vertical wall. Three vertical walls were built and equipped with a sealed structure on the backside; the walls were made with perforated bricks. The walls were covered with different evergreen climbing plants: Pandorea jasminoides variegated for the first wall and Rhyncospermum jasminoides for the second one. A third wall was kept uncovered and used as control. A data logger and sensors were used to measure and collect the temperature of the wall, on the surface exposed to the solar radiation and on the inner surface protected by the sealed structure, the external air temperature, the wind speed and direction, the solar radiation falling on the wall. The experimental tests showed that during the daytime of warmest periods the use of the green walls allowed a reduction of the external surface temperature registered on the walls shielded by the green systems: the temperatures observed were lower than the respective temperatures of the control wall of about 3-4.5 °C. During the nighttime of coldest periods the use of the green wall allowed to keep the external surface temperature of the walls shielded by the green systems at values higher than the control wall ones: the temperatures observed were higher than the respective temperatures of the control wall of about 2-3 °C.