Originally Posted by
MadJohn
How much ventilation you need is directed by many things. The bigger the fan, the lower speed you need to run it on to get the same CFM. You may need to run that 5" on 100% to get it to shift enough air whereas you'd only need about 20% of a 12" fan for the same airflow. This will make it much much quieter to run the 12" over the 5" and possibly a bit cheaper too. However the tent might not have a 12" opening (never seen one that does) and cost rockets as does space requirements (bigger fan means bigger pipe). But sound aside there are other considerations.
The efficiency of the fan (not all fans are equal), the ambient temperature of the room, are oyu venting into the same room the tent is in or are you venting externally. Is your intake being fed air from outside or inside all affect how much air you need to exchange. Finally the light you choose affects the heat generation and so how much hot air the fan is going to need to contend with.
It's a lot to consider I grant you but that's what the inputs are.
All that said, best advice is if money is no object then get the biggest fan your tent/room/budget can accommodate and you'll not go wrong. Bigger is quieter, has plenty of head room if you need to turn it up and will mean if oyu do upgrade again you shouldn't need to worry about the fan. Just remember you have to think about accommodating the exhaust somewhere so that needs to factor into how big you can go.
As a side note I am a little confused why you have both an extraction fan and an inline? Commonly I've seen people have a pressure balancing inlet fans to stop tent walls from curving in and filter inbound air but usually the inline is just piped straight out of the tent to the exit. Why do you have both?
MJ
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