###### Abstract
Generally speaking, apart from all the design strategies typical of the principles of bioclimatic architecture (such as, for instance, space organisation, wall-window-ratio, orientation, thermal mass, operation management [19,20]), more relevant energy savings achievable in buildings can be attributed to two main categories of components: technical plants (HVAC system) and the building envelope, which have a synergistic relationship. In fact, a reduction in energy consumption related to the HVAC consists in the use of active systems which entail further energy consumption. As regards the building envelope, passive systems (not energy depending) can be used, which allow to actually obtain a reduction of the energy consumption (and at the same time, to also save on the use and the size of the HVAC system). Clearly, the occupants' behaviours and attitudes might also significantly influence energy saving, as demonstrated, for instance, in [21, 22, 23, 24]. Starting from the above considerations, in this work, it was decided to pay attention to the use of a passive system to be applied to the building envelope, that is, green roofs equipped with different vegetation types. Among the passive systems, green roofs are becoming more and more popular due to their capability of reducing the energy needs for the climatization of buildings [25, 26, 27], especially for cooling purposes [28, 29, 30]. At the same time, vegetated roofs also have a positive impact on the outdoor urban environment in terms of regenerative sustainability, allowing to induce various environmental benefits [26,31], such as reducing air pollution [32,33], mitigating noise [34,35], improving the management of runoff water [32,36,37], easing the urban heat island (UHI) effects [38, 39, 40], and increasing the urban biodiversity [41,42]. Moreover, the European Union is evaluating the possibility of including criteria specifically referring to green coverings within the EU Ecolabel scheme for buildings [43]. In addition to experimental studies [44, 45, 46], the effect on the built environment of vegetated roofs in diverse climates has also been investigated from analytical [47, 48, 49] and modelling points of view [50, 51, 52] over the years. In particular, the relevant parameters for energy modelling of green roofs have been explored in the literature, particularly referring to the role played by leaves and solar radiation in the thermal exchanges between vegetated layers and the surrounding environment [53]. The reported literature indicates that green roofs represent very promising building components, also in the Mediterranean context, as demonstrates the incremental number of studies and analyses carried out in recent years concerning both the experimental [44, 54] and the simulating approach [47, 55]. Other studies have underlined that additional issues would probably need more attention regarding plants growing on the roof, especially their influence on the thermal performance of green roofs [56; 57], and the influence of the evapotranspiration component on the green roof heat and mass transmission [50; 58]. Taking into account the studies reported above, it is evident how green roofs can have a strong impact in attenuating the average radiant temperature on building roofs [44; 59; 60]. This capability of acting as thermal insulation positively influences the indoor comfort conditions for the occupants of the rooms sited under the roof [27; 45; 61; 62]: this aspect has always been critical in the design phase of a building envelope. [PERSON] et al. [63], by means of a field experiment performed in a school building in Taipei, have developed a finite element analysis model for the improvement of indoor thermal comfort in the presence of extensive green roofs. The researchers found a decrease of the indoor temperature up to 4 \({}^{\circ}\)C, compared to bare roofs. [PERSON] et al.