I have a new grow room which is 4x10x8. At the moment I just have a 6" extraction with 4" passive intake, but I know I need to make this bigger. I also have a portable AC unit in there so with that blowing out so much how am I going to keep positive pressure with a bigger passive intake + AC running at times? Any help is appreciated =) EDIT: I MEANT NEGATIVE PRESSURE, DERP.