if you can exhaust to the atic do that. as for fresh air, the exhasut fan should cause negative pressure in your closet, this will cause frewsh air to be sucked in under the door. Also i think i saw that you have little panels that slide in an out to make shelfs that can go higher and lower. I have the same thing and I find that as the plant grows it is easier to start it a foot or so high and then move it down the knotches as it grows, this captures all the light in a smaller space so less is wasted. Im not sure if that made any sense but when i get around to taking pics of mine ill show you. Also you prly want to make a cool ube for your light. a glass cadel cylinder and a computer fan is what i have, and it keeps the bulb at a temp i can touch with my bare hands. thats a nifty closet you have, and it looks like the perfect place for a real tall sativa. good luck.
