Well, since this is my first grow and I am only in the seedling stage, I can't give great advice. But I did cut a hole in the ceiling into the attic and ran flexible ducting to an inline 170cfm fan, I also have a 4 inch carbon filter that I'm praying will be enough for the smell. I bought some panda film to section off my grow area, its white on one side, black on the other. I am not really sure if my ventilation is gonna be adequate, I was on a tight budget and bought whatever i could afford. Only time will tell. If you can't cut holes, I dont know what to tell you. I dont have any intake into the closet because there is a nice gap under the door that allows for airflow, but adequate ventilation is neccessary for controlling heat and providing the plants with fresh air.