Caculating exhaust CFM (small box) - confused

E

efp

Active Member
Hi all,
I know that to figure out (roughly) how much CFM my fan needs to exhaust adequately, i need to use the following formula Length x Width x Height = Cubic Ft, then Divide by (5), (6), (7) or however many minutes you want new air to be replaced.

Box dimensions are: Width 32cm, Length: 77cm, Height: 81cm
Using those numbers i get: 199584 [cm3] which is 7.04824 [ft³]
The next part is what gets my confused. Dividing 7.04824 / 5 = 1.409648 which gives me a lot of decimal places. Does that mean i need 14 CFM? I dont understand. :wall:
 
tip top toker

tip top toker

Well-Known Member
It means 1.4cfm. If it moves 1.4 cubic feet in a minute, then in 5 minutes it has moved 7 cubic feet of air, so it has exchanged the air in the grow room.
 
  • Like
Reactions: efp
E

efp

Active Member
efp said:
Hi all,
I know that to figure out (roughly) how much CFM my fan needs to exhaust adequately, i need to use the following formula Length x Width x Height = Cubic Ft, then Divide by (5), (6), (7) or however many minutes you want new air to be replaced.

Box dimensions are: Width 32cm, Length: 77cm, Height: 81cm
Using those numbers i get: 199584 [cm3] which is 7.04824 [ft³]
The next part is what gets my confused. Dividing 7.04824 / 5 = 1.409648 which gives me a lot of decimal places. Does that mean i need 14 CFM? I dont understand. :wall:
Click to expand...
Wow, 1.4CFM! HA. Crazy!
So in terms of air exchange, one exhaust PC fan would do fine. Right?
 
You must log in or register to reply here.
Top