You do not nescesarilly need ventilation, for instance if your using only fluoros .. fluoros throw almost zero heat . plants like what u like, comfortable temperatures, if you were say using a 1000k light in a large room that had central air , you still probly wouldnt need a vent. But if u had a 1k light in a 4x4 box u would definately need a vent. All depends on what your using to light it, and size of grow area, and if the room has ac going to it etc..

And would also like to add , having larger pot makes less maintenance = less watering.