How often do I need air to be exchanged?

I just bought a 5x5 gorilla grow tent and trying to figure out which inline fans to purchase. I will be using a 1000w MH for veg and 1000w HPS for flower. Is a 6" 420 CFM intake at the bottom of the tent and a 6" 535 CFM fan for exhaust attatched to a carbon filter overkill? I want the exhaust to be higher CFM than the intake for negative pressure right?

Negative pressure for sure. How tall is the tent? 6ft=150cft 7ft=175cft

Massive overkill. But it will be hot. Cooltube? I'd clear at least twice/min.

I believe it is 6-7 ft tall

Man just get a speed controller for at least your intake, or both intake and exhaust if you can and just play around with them until you get it honed in.

I have a 6" hurricane rated at around 500 cfm for my closet that's half the size of your tent. You can't really go overkill with exhaust IMO, but I'm no expert

Highocaine said:

Negative pressure for sure. How tall is the tent? 6ft=150cft 7ft=175cft

Massive overkill. But it will be hot. Cooltube? I'd clear at least twice/min.

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So if I need to clear a 5x5x7 room twice/min that is 175 CFM x 2 or 350 CFM? Should I do 350 for intake and 420 for exhaust?

ThorGanjason said:

Man just get a speed controller for at least your intake, or both intake and exhaust if you can and just play around with them until you get it honed in.

I have a 6" hurricane rated at around 500 cfm for my closet that's half the size of your tent. You can't really go overkill with exhaust IMO, but I'm no expert

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Thanks, I will look into the speed controllers, especially since I want to increase the size of my grow in the future, might as well save money and buy a big one now. Any recommendations?

You only need the 350 exhaust, and run passive intake. At least, that's how I roll.

I have the same setup you're trying to achieve. I have an 8000 BTU portable AC that I've retrofitted to an 8" piece of duct that supplies my tent with fresh cool air while the lights are on. Temps never exceed 82 doing this and usually hover around 77. I also have a 6" fan located on the outside of the tent that connects to my reflector. I have one 4" fan that I use as an intake into the tent and another 4" on the opposite side that I use as exhaust. The intake and exhaust fans are only on when the lights are off to keep humidity around 50-60. Your reflector fan and AC should only come on when lights are on. Works great for me and I live in SoCal so summers here get pretty hot.