Two questions in the same day...I may have more still :)

Has anyone taken the time (maybe Nick?) to determine if there is a major
impact due to leaving walls of adjoining shells as exterior instead of
changing them to interior, air-walls, or deleting them? I only ask because
I have a 4M+ SF building that is requiring 20+ shells stacked and adjacent
and I'm looking for every time saver I can find. I simplified the shells
as much as possible, but due to geometry this is the smallest number I can
squeak by with from an orientation/geometry/overlap.

I should note, this is an existing building and the model is being more or
less calibrated, so just having a rough idea of the impact of this nuance
will allow me to decide to take the time or to chalk it up in my model
error.

Thanks much!
Jeremy R. Poling, PE, LEED AP+BDC