The indirect green façade, where vegetation is supported by an
HPDE mesh or by a steel mesh, can be considered economically
sustainable for the best scenario; differently in the middle scenario
only the greening system based on the HDPE mesh (2A) is sustainable
(Table 7). In particular, for this system positive NPVs vary
between 2061V (middle scenario) to 14,713 V (best scenario; Graph
1) with IRR values respectively of 5.2% and 5.8% (Graph 2) and a PBP
of 33 and 16 years. The indirect green façade (2Ae2B) compared to
the direct one (green façade) (1) has higher installation (due to the
supporting system) and disposal costs; this happens especially for
the indirect green façade supported by a steel mesh (2B).