How do I model a naturally ventilated double skin facade in proposed and baseline building?

- proposed building: as designed, with a thermal zone for the intermediate area. The insulated exterior wall is located between the building interior and the intermediate area, the "double skin" is a lightweight uninsulated construction between intermediate area and outside.

- baseline: with or without the double skin?

For the baseline building, I have to limit the vertical fenestration area to 40 % of the gross above-grade wall area. If I model the baseline building with double skin, is this based on the outer shell or on the inner shell of the building? For me, the logical solution is the inner shell (this is the insulated shell), but our software support proposes to do it based on the outer shell.

I found an old post from 2013: "We faced this issue for a project in Italy which is now certified. Essentially we removed the outside of the double facade in both models and reported those results in the form. In this way we are not violating the modeling protocols for zoning or area. We then added the double facade to the proposed model and submitted the savings as an exceptional calculation (one reason to do an exceptional calculation is that in order to show savings you need to violate a modeling protocol)."

This sounds interesting, but it would be nice to have some confirmation of others who have done it like this.