is the lowest point from the floor to the ductwork?
Can you place the wall and door in any other more suitable and fitable space to still achieve your desired plan?
Are you going to stay in your home for a long period of time? If yes, maybe code requirements need not be met on this specific project.
Just some thoughts.
I am not a person that bypasses code laws, but in your case, it could be done easily. Then when you move or sell, you would have to remove the door even if its contested.
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