both the intake and exhaust are 4" and they are rated at 80cfm There is not an additional fans in the closet. I thought the thermometer was supposed to be close to the plants.....should it be above the lights......? I'd rather not add more to the closet.....second intake fan, third fan in the box, etc..... Is there a way to change my current config so that it works right? What if I take my intake ....move it from the bottom of the closet and put it at the top and use it as a second exhaust, or will I still need a fan in the closet to move air around? As far as how to the plants look.....Haven't got to that step yet. I want to keep testing the grow box to make it right before actually starting.......getting very impatient.