It's half a small basement and I'm real big on air exchange. I have it designed so the hot air leaves the room and the cold passive air intake is on the other side of the basement (coldest part of basement). The passive intake is a 20x12" hole cut into the grow room with a furnace filter attached. This forces the air to circle through the basement in a counter clockwise way. The other half of basement which is not finished acts as a heat sink.
One 12" can MAX fan 1700CFM exhausts the room through Can 125 filter while lights on. Straight ducted out, no bends or elbows.
One set of AC hoods is closed loop with a 400 CFM fan pulling air from outside the basement room to upstairs bedroom. (not nature outside)
One set of AC hoods is hooked to another CAN 125 filter within the room with 800 CFM fan going through 2 hoods and out to another bedroom upstairs.
It's less than 8 degrees outside right now, my furnace doesn't run while lights on and it's 70 degrees in my house.
Room is 19x9 with 7.5' ceiling.
Nice set up...
Where I'm at is a little different. I have a small 7 X 7 room in a basement and I live in a place where the temps, in winter, can go from -30c to +5c (-22f to 41f) overnight.
So I run 6" 400 cfm fan to cool 2 hoods in a straight shot from outside the tent, through the hoods and out a window, that has a backdraft damper.
I also have a 4" 170cfm fan run at 3/4 speed to exhaust the tent (not heat, but smell)
And I have a 4" 140 cfm fan bring in fresh air from outside into the tent. (I aimed it at the ceiling then have a 12' circulation fan aimed at that to disperse it.)
When it's -30c outside I have a good balance in the tent and my A/C doesn't run at all. As the outside temps warm up the A/C works harder. When it gets to +5c then the A/C has trouble keeping up with my lights.
The trouble with a small room is that even small changes in everything are magnified into big things....
