Green Roof Technology

Green roofs alleviate UHI effect through the raising of surface albedo [41] and, so, can reduce the air temperature through evaporation [30] and thermal insulation [42,43]. Therefore, green roofs and walls help in the reduction of energy consumption and guarantee an excellent thermal behavior in both heating and cooling seasons with consequent good thermal comfort conditions, thanks to the high thermal inertia technology [44–47]. Figure 5 shows the heat flows through the roof during the heating and cooling seasons, where *Qsol* is the quota of solar gains and *Qsol,n* is the quota of solar gains that enters the system.

**Figure 5.** Schematic diagram of green roof during (**a**) heating season and (**b**) cooling season.

The thermal conditions of buildings and urban environments were investigated at urban scale using two parameters: The 'Normalized Di fference Vegetation Index' (*NDVI*) and the 'Land Surface Temperature' (*LST*). According to recent studies [31,32], the *LST* and the external air temperature decrease more or less rapidly as the green areas increase, depending also on the type of urban morphology. The local climate conditions were assessed before and after the installation of green technologies.
