I'm setting up my 9x9x8' grow room and I just installed a 10" max fan for exhaust (see journal for details: First Grow - 3000w - Ebb & Gro - H&G - Sealed ) . I will also be installing a 10x39" Phresh filter for odor control.

I'm trying to figure out if I need a fan for intake or will making a hole for passive intake be fine?

If i do need a fan would the Vortex 6" 450 CFM be a good choice?

Thanks!

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Nice setup.

I took a look at your journal and saw you have the lights cooled so we are talking about the environment and I understand you want to keep approx 1400 ppm CO2 in there.

What I found in regards to intakes is if the hole is large enough I didn't need an intake fan. Like you I went into the sub floor (4"x12" hole) and out the top. I have dual cabinets so only about 10 sq feet or so but with only one 80 CFM bathroom fan and passive intake the cab stays 5 to 10° below outdoor temps. (light is in diy cool tube 110 CFM fan) so not much heat.

On the other hand using CO2 I am sure when you want to exhaust you want to do it as quick as possible and by matching the CFM to the exhaust in a 9x9 room it would happen almost instantly. with 9 foot ceiling you got like 729 cu ft right?

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Thanks!

Exactly

Good point. If i have an active intake the air exchange will happen quicker and I can fill the room back up with CO2 sooner.

The room is actually 10'6" x 10'6" x 8" so it's real close to 800 cu ft but only about 9'x9' is for growing area.

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Close enough, Just one of those 450 CFM fans will be enough to exhaust it in a couple minutes with say a 4 by 12 intake. Better with two. I am sure you have thought of dampeners on the vents. If you can keep those tubes cool to the touch or close to it the room wont get much hotter then the rest of the house. You will probably be exhausting mostly for humidity. Depends on what temp your starting with. I bet you could set it up for two cycles four hours each with only one 10 minute exhaust in between.

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Waterfarm (completed) Cabinet to Waterfarm (completed) Nute Challange (completed)

LED/T5/400W Cabinet (completed) Dual Cabinet Build (current) Dual Cabinet Grow (current)

Actually the 10" max fan 1000 CFM will be doing the exhaust and the 6" vortex will be handling the intake.

Which brings up another thread of mine that you may have some input on: Backdraft dampers <-click to follow link

The tubes are cool to the touch but they still seem to heat up the room pretty good. Without the AC it gets much hotter than the house real quick. The 8" vortex that I used on the second set of lights is much better than the Dayton 463 that I put on the first set of lights though. The difference between intake and exhaust for the first set of lights is about 10 degrees, while the second is closer to 6. I'll probably switch out the dayton for another vortex after this run.

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I'd say run the setup as is, see how it works for your environment, then make your decision on whether to add an intake fan. In my current situation, I use a passive intake, and it works well enough for me. I'm also not using Co2 though, so the fan is constantly going. What I have done though, is hooked up a Can Fan RS6 to run at "night" instead of the Max Fan so I can save about 120-150 watts.

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This may help with the CO2

"This form will calculate how much CO2 will be needed to fill a grow room to the required level. It will also determine how long it will take to fill at the given rate."

Click Here

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Waterfarm (completed) Cabinet to Waterfarm (completed) Nute Challange (completed)

LED/T5/400W Cabinet (completed) Dual Cabinet Build (current) Dual Cabinet Grow (current)

Good advice. I'll cut a passive and test it out. I love how energy efficient your setup is. Nice work!

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Thanks Cruzer!

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So i cut a 6" hole and installed a non-motorized damper. The problem now is that there is a lot of negative pressure in the room and the intake makes a lot of noise. It practically whistles. I really don't want to cut a larger hole (I've already made swiss cheese of the room) but I may have to. Or purchase a fan. The largest circular hole that I could cut would be an 8" diameter. I'm afraid that it would still make a lot of noise and i'll still have a significant amount of negative pressure. From my understanding (and correct me if i'm wrong) if a fan is constantly pulling against a strong negative pressure the fan will wear out faster. Hmmmm....

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