could you give me a site to a co2 regulator like the one you described? that would help alot. i am growing in an insulated shed. the walls are about 6" thick. for the doors i applied weather proofing rubber to the door frame and to the door it self. then once i latch the door (one latch on top, one in the middle, and one on the bottom) the rubber makes a tight, light proof, seal. when the lights are on at night you cant see the light from outside the shed no matter where you look. i also caulked all the cracks. when my exhaust is on it takes force to open the door. it wasnt always this way, though. it took probably the most work out of the whole procedure.