NPV and payback calculation depends on all the factors shown in Tables 1e3. A sensitivity analysis was performed to determine which costs or benefits cause significant impacts in the overall NPV estimation. The sensitivity analysis was performed for all the green roof types; however, all the analyses showed the same finding: all green roof types are sensitive to the same parameters. Hence, Fig. 14 depicts how a variation from 20% to 20% in the personal
and economic factor affects the final NPV result of any green roof type. Similarly, Fig. 15 shows how a variation in the social factors affects the final NPV estimation.