Best way to measure area not in shadow

[Yvonne]

What is the best way to measure the area of a space not in shadow? If we measure the area via 3D docs in plan, it doesn't account for area not in shadow but is covered. 

For example highlighted in yellow:

Operating system used: Windows 11

[CosminF]

Hi,

The only workaround I see would be to manually get the fill of the shadow, move it on the right by a fixed value, do a fill for the area under the roof excluding the building, and afterwards substracting the second fill from the first one. 
Basically doing this manually - i know it can be frustrating, if the building changes slightly you need to redo this. 

I was also thinking if you maybe could use zones for this (to have them automatically updateable) but I do not know of a 3D "shadow object" that you can use to substract with.