I am planning on building a grow box in the back of the garage. My only concern at this point is how to get the box fresh air without freezing the girls. It gets cold up here in the NE durring Winter. Heck , its cold here most of the time .I am thinking a simple passive system. Fresh air would come in low through an adjustable intake. The stale air would exit high through adjustable vent. Both intake and exhaust would need to be adjustable so they can be dampered down when it gets cold and opened when the outside temp is warmer. Now I am only talking a 3x3x6 box holding 1 to 4 plants. The box will probably not be in use much in Jan, Feb & March. I now have a 400 watt mh/hps light w/ electronic dimable ballast, cool tube, 190 cfm fan and carb filter. I doubt smell wil be an issue due to location and an almost constant breeze ( think lots of woods and inbetween two mountains ). So any thoughts would be appreciated. Please post so I can reply and get my post count up past 50