How Much Fresh Air?

I have a quick question. I’ve seen plenty here about what size exhaust and intake fans are needed. But I don’t understand how much air can be recirculated back into the tent. (I’m gonna use my 4x4.)

For example, I could run my exhaust duct around to blow into one of the intake holes, and I wouldn’t lose too much of the heat generated by my light. I’d like to keep some of that heat in the winter, since my tent will be in my unheated basement. I figure I can leave a gap between the end of the exhaust duct and the intake so there will be some fresh air going in. Any suggestions about this?

And what kind of cues do plants give to tell their people that they aren’t getting enough fresh air from the room into the tent?

Total noob question, I know, but that’s what I am, lol. You all are great. Ive learned everything i know here, just getting geared up for my first indoor grow amd learning everything I can.

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Manage your airflow such that your temps and humidity are managed and you’ll be golden.

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I run a supplementary fan on a timer to inject fresh air into my grow space. I have another fan set on a thermostat to vent the space for heat management. This combination provides plenty of air. You need to look at your setup to see if you can configure it the way you want it.

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I run a 4x8 tent.
I use a 6" exhaust on a temp meter that turns it on at 82F shuts off at 80F. Oh don’t use my temp range it’s a bit high for most lighting. I actually do 85f if it can get there but due to colder temps outside it only hits 82f.
As for intake I just have 2 vents open and air flows in when exhaust fan is running.

But as stated above an intake fan on a timer would be a nice add on.

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Oh cool. So I don’t have to worry too much about drawing in a bunch of fresh air?

That’s a good idea. I think I’ll do a variation on that. Thanks.

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I like that. I feel much better now. I was stressing too much about the intake.

Its definately a plus to have but for cost reasons I didn’t add an intake yet. I will add on next grow. Plants are doing fine without it. They will most likely do even better with one.
Snap I could put an intake fan plugged into same controller as exhaust. Hmmmm. Here come the upgrades

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Ha! I like when I get breakthrough ideas like that.

You need the co2 specifically. That’s what the plants use. If you recycle warm air you wouldn’t be replenishing the co2.

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@dbrn32
I was stating I could use same controller if I upgrade and use an intake fan also.
Would be a separate fan for intake that would only cycle when exhaust fan is running. That way the only time humidifier would run is when fans cycle.
If I have intake cycling at a different time it just makes more work to control humidity.
Exhaust fan runs out of tent and thru wall into adjacent room. Intake can be from same room away from tent.

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You mentioned a complete air exchange every 90 seconds, right?

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Do you have an estimate as to how often I would need a complete air exchange in a. 4x4 tent to keep CO2 levels adequate? I know there’s variables. I’m just trying to get a rough idea.

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I think its every 2 minutes, but definitely somewhere there about.

@BetrayedSoul, it doesn’t really matter how you get there, as long as you get there. I have only been able to stay at ideal by controlling temp/rh of the room my intake air comes from.

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You need to figure volume of tent. Length x width x height in feet will give you feet³. Then size you ventilation accordingly. If you have 200 ft³ and are moving 200 cfm that’s one complete exchange per minute.

Keep in mind that everything attached to your fan will effect its ability to move air. Duct, bends, filters will drop cfm of a fan a lot.

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So having a heater in the tent would be pretty pointless, because the heater wouldn’t even be able to keep up, and it would effectively end up heating my basement. Ok. So I would be better off partitioning off part of my basement that the tent is in, insulating it some and heating the whole space.

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Probably. Every situation is a little different, but I would expect you hit nail on head.

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Ok. Now I have a good direction to look. I really appreciate everyone’s input. Would anyone here mind if I tagged them into my grow journal when I get started? It’s going to be a few weeks.

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Hit me up.

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I definitely will.

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