Overall, the basement area is about 18'X20'. I have 400w hps lighting and a hydro sys that uses lava rocks. I was considering the Growlab GL120 w the accessory Kit that has a Can Fan 4" Centrifugal fan coupled with a carbon filter (Can-Filter 9000). I realize it would be more economical to make my own but this unit has the frame and the fan to make it a little easier on my first attempt. I was going to exhaust directly into the open area of the room. With just this 4" exhaust fan do you believe I'll be able to keep temp down during the veg state of around 18 hours?