Duct fabrication parts need an option to show internally lined + externally lagged insulation simultaneously.
This scenario happens on a regular basis.
There can be situations where external firespray is also applied plus perforated metal lining over internal insulation.
Not sure if this is unique to the Australian market & standards or if it also applies in Europe / USA?
If it does not apply in USA I wouldn't expect this idea to receive many votes & therefore don't expect it to be implemented.