Definitely maintaining negative pressure. Intense vacuum on my panda film.

My "closed loop" simply means that the vertitubes heat never enters my room directly. My room is partitioned off in just panda film. I pull outside room air into the top of my growroom, straight down through the vertitube and immediately back out of my grow area. Then its exhausted out into my house. I have no attic space to work with. This is the reasoning for this.

Thanks