I have 2 of my rooms linked together, sharing a single 5000 BTU a/c that is located in the flower room.@politoed
Okay so here’s my train of thought, I’m in a basement so my setup will vary since heat is a non issue.
The intake from downstairs this is a passive intake? And an active intake with the wall AC unit?
Weather will play into the humidity factor huge, good news is you’ll be wanting the Veg room higher in humidity anyways. With that being said I would think the fan will have to work harder to pull the air through the filter. They say you’ll want 1 full exchange of air every 1-3 minutes. So 200CFM x .8 (not exactly sure on the reduction factor) puts you at 185CFM still within the 1-3mins full exchange. Portable humidifier? I’d put the humidifier in the veg area for the time being.
Let’s move on to the flower room, 450CFM x .8 is 360CFM the total area of exchange is 430CFM (both rooms) assuming you either synchronize the 2 inline fans on timers or run them all the time. The fan won’t have to work as hard since it’s piggybacked that way and still within the 1-3mins exchange. Dehumidifier in the Flower room. Since it’s gonna get thick in there mid flower with perspiration. Shouldn’t be an issue as long as you got fans moving the air around. As far as cross draft goes I think the layout in the picture is set up pretty well.
The drying area I’m going to assume as roof vents to let the air escape, I’d maybe consider installing a whirlybird on the roof to help draw out the air more actively than passively. Cheap, easy to install and completely natural on a roof.
Those are my thoughts, I’m not going room to room with the air exchange, so I could be a little off. I think @Preston9mm goes room to room maybe he could add I little more insight.
A 400-ish CFM fan (6") sucks air from the flower room & dumps into my veg box, the veg box has a 200 CFM (4") fan that pumps air back.
Both rooms balance out to within +/- 3°.
Each room has a couple passive air flaps that allow the room to breathe. I'd consider an air conditioner as an active air intake. It's drawing from outside & forcing air in.