## 3 Results and Discussions
### Outcomes of Energy Simulations  
Since the main aim of this work was to assess how the use of green roofs can affect the indoor comfort and the energy consumption of a building, it was decided to report, in the first part of this section, a comparison between the simulation results of Scenario #1 and Scenario #3. In particular, considering that such estimation is affected by the temperature changes during the actual HVAC system operating periods and in light of the detailed schedule utilized to run the simulations, it was chosen to divide the resulting data into two five-days periods representative of winter (Figure 9, on the left) and summer (Figure 9, on the right) conditions. Specifically, in Figure 9, the green lines represent an average of the values obtained for the six plots (Scenario #1), with its relative ranges of variation and the blue lines represent the standard case (Scenario #3); on the other hand, the red lines indicate the HVAC system start-up intervals. Looking at Figure 9, it can be noted how after an initial start-up phase of the HVAC system, the presence of a green roof during the winter season does not seem to improve the indoor thermal conditions, while during the summer season, it brings a noticeable improvement of the indoor comfort levels. It must be underlined here that the amplitude of the variation range relative to the green roofs'  
Figure 9: Comparison between Scenario #1 (green lines) and Scenario #3 (blue lines) for winter (left) and summer (right) conditions. temperature values is due to the fact that as reported in Section 2.2, the six plots are characterized by different features and therefore, describing parameters; in particular, the type of species and its relative coverage percentage have a strong influence on the monitored temperatures. The temperature differences noticed also had an impact on the energy consumption. Over the representative five-day periods considered, in fact, a 18% increase for heating needs (220.05 kWh for the standard roof against 259.59 kWh for the green roof) and a 44% saving for cooling needs (189.38 kWh for the standard roof against 106.37 kWh for the green roof) were observed. As mentioned earlier, after this first comparison, the authors wondered what results would have been obtained by simulating a green roof similar to the real one using the green roof configuration tool provided by EnergyPlus. The second part of this section shows, therefore, a comparison between the results obtained from the Scenario # 1 and Scenario # 2 simulations. Similarly to the previously reported Figure 9, Figure 10 contains the obtained results for the two five-days periods representative of winter (on the left) and summer (on the right) conditions. In particular, the green lines (Scenario #1) and the red lines (HVAC system start-up intervals) are the same as shown in Figure 9, while the black lines represent an average of the values obtained for the six plots, with the relative ranges of variation, using the Scenario #2 EnergyPlus settings. By analysing Figure 10, it can be seen how, in the winter conditions, the green roof simulated according to Scenario #2 shows a very similar behaviour to that in Scenario #1, particularly during the air-conditioning working periods. In winter conditions, however, Scenario #2 allows to obtain higher temperatures than Scenario #1, corresponding to a further improvement in the indoor comfort levels. Furthermore, in summer conditions, contrarily to Scenario #1, Scenario #2 shows an evident very variable temperature trend between day and night, typical of a context highly influenced from solar radiation, which does not seem to reflect reality. As for the fact that the changes of the Scenario #2 temperatures range are much narrower than those in Scenario #1, it must be observed that this is most likely due to the fact that, as previously highlighted, the model used by EnergyPlus does not allow to set all the parameters of the green roof freely but imposes some constraints to their numerical values.