I want to keep dust from coming into the living area from where they will be working on the addition. I put up a zip wall (plastic barrier) in the hallway to block dust - but I noticed that when the central a/c was running, the large grate single return was pulling air past the plastic sheeting and didn't allow me to properly seal the sides b/c the rush of air was going past the sheet. I tried closing the air supply in those rooms and it helped a bit but I would guess that even if I taped up the sides, the air would still flow through, along with the dust.

Long intro but my question is, what can I do to keep dust from coming from the addition area while the A/C is on? Do I not use the a/c?