As a side note...this is not my design by choice as you could guess, but rather a situation the building owner wants to do and so we're researching it for him. My first solution was, of course...uhh, shut the door.
Thanks for the info everybody.
Is this as simple as the balloon has a terminal velocity in air...the same as all other objects falling downward? The direction the balloon is traveling doesn't matter--it will slow to its terminal velocity.
What are the effects from keeping the front doors to a store open during the summer cooling months while trying to condition the space? (5000 sq ft) I am running into problems finding exact formulas for calculating wind and external pressures vs. internal building pressure through the open...