From my experience, growing plants with the doors closed during dark periods with no ventilation does effect growth substantially. I had a tedious grow a couple years ago in which I opened the door to my hallway "grow" closet at lights ln to bring in cool air and keep temps down and shut the door at lights out. I had an oscillating fan inside. Plants grew like shit and took way too long to finish. And lord forbid if you accidentally leave the door closed for lights on, plants would be fried. Find an old pc fan or something atleast and wire that shit up, your plants will suffer in the mean time. Good luck!