Passive Cooling Techniques for Less Energy Consumption in Buildings a Comparative Study on Green Surfaces

The increase of power peak and energy demand during the cooling season is becoming a crucial issue; for this reason, in the last decade, new passive solutions for optimizing building summer thermal behavior have been developed. In particular, green surfaces have been regarded as useful tools to provide energy savings in buildings and mitigate the Urban Heat Island (UHI) phenomenon, being capable of substantially reducing the roof surface temperature and increasing insulation power of surfaces. Green roof and green living wall thermal performance has been extensively studied, but the specific effect of substrate moisture and insulation deserve attention. This study investigates green surfaces energy savings in Mediterranean climate, related to insulation thickness and substrate moisture. The thermal behavior of a green roof and a living wall located in Brescia and Cosenza, Italy, are assessed through energy dynamic simulations in Energy Plus, to depicts how these passive technologies can improve the energy performance of residential buildings in different localities of Mediterranean; city of Brescia is in fact characterized by a continental climate, while city of Cosenza is warmer. A typical Mediterranean residential family storey house is implemented in Design Builder to simulate the application of green surfaces. The scope of the work is to identify the best roof and envelope configurations, related to insulation thickness and water content, to obtain the maximum building energy saving both in summer period and annual one. Simulations show, both in continental Mediterranean climate and warm one, green roof and green living wall can reduce the cooling energy consumption in buildings and in general the annual energy demand.