Here's the deal....I'd like to exhaust the air, but frankly... I'm scared I'm gonna fuck something up and be left with a gaping hole in the floor or ceiling.

I understand the concept...pull fresh air in from the floor, pull air out through a carbon filter so your air is cleaned as it's exhausted. I'm a little worried about temps. I leave the door to the closet open about a foot, and temps stay around 80. I leave the door to the bedroom locked. Well it's getting cold here now... and I'm only running an 8 tube FLO fixture so it doesn't put off heat like MH or HPS's.

Would my temps get too low by flowing cold air from outside through my closet? What about at night when the lights are off? Surely they'd freeze, right?