How do you calculate max cfm for a certain volume of ducting.

[IshmarRodriguez]

I have 12' of 4" ducting. I want to know the maximum fan CFM I can put on the duct to exhaust my grow room without causing air to blow black against the fan.

Are these Vortex fans worth the money over Inline Fan? What is the best way to cool a 4'x5' enclosed room running a 1000w HPS on a cooltube, ballast is located outside the room.

Thanks for the help!!

 

[IshmarRodriguez]

This is such an awesome question, anyone know? We just got a inline jet fan anyways. It seems to be working without much resistance coming back.

 

[flyfishinrock]

I think there is too many variables for someone to guess. Every bend in the ducting, depending on degrees affects the cfm of the fan. I would imagine the type of elbow also does, add a filter and who knows.