ventilation/fan question

[chrisouth]

i understand stacking case fans isnt the best method. i was wondering if i built a air proof box with 2 case fans ( one on each side) and both blowing in the same direction with a piece of square to round duct connected to the box. the square end covering one of the fans screwed into the box and the round end connected to carbon filter. would it keep the all available cfm's ?

[redtails]

No, anything you do to the fans will decrease the cfm's: e.g. ducting, square to round adapters, too much/too little spacing between the fans, etc. I have a 130cfm fan (4" round) exhausting the heat from my 2x2x4' box (16 cu ft) through a 90 degree bend, 4"-3" reducer and 6' of 3" flexduct (what I had) into the attic and it keeps it perfect. You really don't want to go lower than 100cfm at the minimum, I had to play around with 3 different fans to get this result.

[frostedwonder]

Hey just thought you may enjoy one of the stickies on grow setups. It kinda covers a wide range of things but its worth a look. http://boards.cannabis.com/growroom-setup/112273-fans-not-just-blowing-hot-air.html#post1381660