I was thinking just a passive intake at the base of the door, i am not sure what size they should be but i was thinking two 3" to 4" holes. I want it to be pretty quite, or as quiet as i can get. I figure by mounting the vortex fan in the attic i can keep the sound down, but now that i think of it i am not sure if it could survive the summer in the attic, its gets really hot here. Another thing is i am not sure how tall i should make my flower chamber. i know the Hps needs to be around 18" from the plants and the ballast is about 10 inches tall, it sounds like i am going to be limited in space so maybe Scrog would be best for me after all. i will have to do some more reading about that technique. thanks for the input wman44.