I have a 5'x5' closet setup with 2 1000 W lights, an HPS and a MH. I use a 600 something cfs inline fan to exhaust two 6" AC cooled vents using a 6" tee.

My question is this: would it be cooler to have glass on the vents and have the cool air pull through the other 6" exit or would it be cooler to remove the glass and plug one of the 6" holes so that the air would create an upward draft?

note: I am using the ambient air and do not have an outside source of air for heat removal.