Oh it's pretty air tight. I closed my rear bunk the other day with this method. Now mind you, the front bunk was still open (but windows zipped closed) and when I closed the door and turned the fans on it sucked the canvas right inside the tent! When I opened the door to go outside and close the bunk end, it was like a cake falling...but as soon as my husband closed the door, I stood at the bunk end outside and it was pretty awesome...it sucked that canvas right into the camper again. I closed the end up effortlessly. I can only imagine it will be even more effective when I close up the front bunk while the back is already closed. :0
I guess they are more airtight than you think, Rrick. Mine is a 201423IKSS.
2014 Rockwood Roo 23IKSS
2012 Dodge Ram 1500 Hemi 4X4
Me, Hubby and Luna the Lab