Need specs. How big a room, what lights, what distance is the light from the plants? What temps, what humidity levels?

Usually folks just use the exhaust fans at the top of their cabinet/grow room to expel the hot air. Not usually a need to use an intake fan, unless the room is sealed so tight as to restrict inflow. Even then, just a hole or two down low to let cooler air flow in on it's own.
What measures are you using to keep the plants hydrated?