Question on intake/exhaust fans

[TinyDancer]

So i bought 2 120mm computer fans that push out 134cfm. My original plan was to put one at the bottom for my intake, and the other up top for my exhaust. I am wondering though if it would be better to just put one fan at the top and make a bigger hole in the bottom? My box is 6 sq. ft. so that should be enough air moving out correct? Can anyone point me in the right direction on this? Thanks!

 

[CannaRebel]

I would advise you to put both fans at the top and just cut out small intake holes in the bottom of your box.

What is the output of each fan? 134? or the is the total of two = 134?

Also for ventialtion we are concerned with Cubic Feet, not Square Feet, figure that out then multiply it by 3 to figure out the minimum CFM rating you need. (U need to cycle the air in the growroom more than once per minute)

The logic behind this is as follows:
if your box is airtight and you have two fans say with 134CFM each; then mounting one as exhaust and the other as intake will give you only 134CFM total for the box. Putting two Exhaust fans instead will give you 268CFM total while using passive intake (just cut out holes that are 20% larger than those for the fans). air coming in doesn't count as ventilation if you can't exhaust it

Hope this helped

 

[TinyDancer]

Thanks for the input. Yes both fans are 134cfm each. I figured in order to move enough air 3-5 times in the box i will need 75-125 cfm i believe is what it was. I think i will just go with what you said cannarebel and put both at the top. As far as the holes go at the bottom of the box should i put one on each side or just one on one side?
Thanks!

 

[CannaRebel]

It doesn't matter much, one on each side will allow the air to mix better in the box I think.
Don't forget to add light traps on the intakes as to prevent light leaks.

 

[TinyDancer]

ok sounds good. ill put one on each side. i think im just going to use some cardboard for light traps. i'll post some pics when i get finished working on it!

 

[CannaRebel]

Good luck!
Happy to have helped