As per the results shown in Fig. 1, with 90% of confidence, the personal sector will obtain a benefit of up to $3606/m2 ($331.75/ ft2). However, the most probable NPV benefit is $291/m2 ($26.77/ ft2). Additionally, there is a probability of 1.0% that the NPV result a cost, not a benefit. Therefore, there is 0.82% confidence that extensive green roofs could cause losses up to $25/m2 ($2.3/ft2).