I am not that familiar with the placement of the AC duct on the Bunkhouse, but I used "Seam Seal" from Walmart in the camping section to seal the seams on my new Roll-A-Home when I got it home last Oct. and did every seam with it. It goes on easy from the inside, and places where I thought would be high usage I put a second and third coat on. The bad thing is that it needs to sit open for 24 hours, but I had mine set up in the barn so there wasn't any chance of it getting wind, and wet. Not an option for all I know, but if you do it on a good hot day it will cure in just hours in stead of the whole day. May be worth looking into at least. One note: if the seam is the slightest bit tacky to the touch after a couple of hours it isn't set, and don't fold it up!!! Waite longer.