There is not much information about getting total duct area. As far as I know, the only way calculating duct area is summing scheduled straight and fitting duct area. But some fittings like elbows do not have area properties. What I do is, define a shared parameter and modify the family to calculate area with a formula. But it is too much work to get one number. Am I missing something?
I would like to see total duct area when you check the duct system, as system flow and static pressure.