stack next to a room in the stair case

[p1234567]

hi there,
I am designing natural ventilation to office building.
the office had windows that open max 10 degrees.
so, I proposed adding two stacks(shafts ) one on the external wall with holes as opening. and one in the staircase next to the internal partition wall.
I wasn't able to insert holes in the stack as apache consider it external.
what should I do?
the stacks have opening on top to provide supply and exhaust to the openings in each floor
please advise.
in addition, for balancing air flow in each room. calculating the supply and exhaust from people inside how to take into consideration of window flow? or no need ( I have equivalent windows on each side)
thanx