not really sure.. been surfing the net for designs... its more tall than wide so i was thinking maybe two holes... one at the top and one at the bottom.. maybe two fans one blowing and one sucking it out... i'm a keep my box onmy back porch, i have electrical outlets back there.. idk how much being outside already will affect the ventilation, but thats what i'm thinking bout now.. oh yea and it cost 100.00no, the main thing you need is good ventalation, how do you plan venting this growbox?