## 5 Results and Discussion
In the second scenario where property is being sold after construction, the most probable NPV is calculated as USD -16/m\({}^{2}\) and USD -41/m\({}^{2}\) for EGR and IGR, respectively. The most probable NPV calculated in ref. [13] was USD 291/m\({}^{2}\) and USD 611/m\({}^{2}\) for EGR and IGR, respectively. However, it should be noted that the corresponding analysis, presented in ref. [13], included additional benefits in the form of avoidance of infrastructure cost. Moreover, in compared results from the literature [13, 14, 55], the distribution of costs on other RUs was not analyzed. Sensitivity analysis was based on the variance-based method [77] that was implemented in the Python library [78]. Sensitivity analysis is one of the tools in the impact assessment procedure recommended by regulatory documents [79]. The proposed method enables the calculation of the first (S\({}_{i}\)) and the second order (S\({}_{ii}\)) sensitivity indices, as well as total effects index. Besides parameters from Table 4, additional significant factors are taken into account in Table 6. First-order sensitivity indices of parameters for NPV indicate the greatest influence of the property value increase on the outcome, while the benefit of the heating energy reduction is only significant for models 1 EGR and 1 IGR. This is due to the poor current state of the thermal envelope of the building, but this effect is less pronounced in models 3 EGR and 3 IGR. As is the case with similar numerical analyses, the discount rate also has a notable impact on the formation of NPV results given that the life cycle of a green roof is high. Second-order sensitivity indices, which determine interactions between parameters, are insignificant for the presented analysis and hence the total sensitivity indices are close to the first-order. It is clear that the estimated life cycle period, within a range from 40 to 55 years, also does not significantly affect the outcome, although the membrane longevity parameter has a higher probability to occur twice for a green roof with a longer lifespan. That remark is consistent with the shape of the NPV curve presented in Figure 4, which is almost constant after 40 years. For models 2 and 4 (without the benefits of energy reduction), the most dominant factor is the number of RUs and the increase in the value of the properties, respectively. Although installation cost is a parameter with the highest value in all models, it is not the most influential since it is distributed to all residential units. The most influential economic factors in sensitivity analysis in [13] was discount rate, while the property value was the most important non-economic factor in LCC model from private perspective. In the first scenario in [55], the most influential parameters were discount rate and energy savings, while in the second scenario, initial cost and property value increase were the most decisive parameters in the NPV calculation. On the other hand, in ref. [14], the most important factors for NPV were maintenance cost and discount rate. Based on the results obtained in sensitivity analysis, the presented approach could be extended to different typologies of buildings in future research as it would give different absolute and relative values of parameters in life cycle analysis.