indoor Pepper Grow Tent Air Control

guested

guested

After a miserable inaugural pepper season which yielded a total of 4 ghost peppers and 1 habanero off 6 plants (aphids and overwatering), I'm planning on moving the operation into a grow tent for the winter and hopefully produce in there.
 
I have a 4'x4'x7' grow tent set up in my garage and have a few questions about air control during the winter. The ambient temperature in the garage will be between 10c (50f) and 15c (60f). I have a small ceramic heater to hang in the tent and will be looking to keep the temperature between 25c (77f) and 30c (86f). I also have a humidifier for the tent looking to keep the RH between 40 and 60%. (The ambient air will have ~15% humidity due to our arid Saskatchewan winters.)
 
The questions I have concern the airflow within the tent as well as fresh air into it.
 
1) Reading many sites on growing in a tent they advise doing complete air exchanges every few minutes due to odor build up and CO2 levels during the night, now obviously they're not growing peppers so odor isn't an issue for me but how concerned do I need to be about CO2 build up in the tent?  Can I just leave a few vents open and call it good or do I need to set up a fan to drive air into the tent? Any air going into the tent needs to be heated/moisturized which adds to operating costs but additionally I'd prefer not to exhaust extremely moist air into my colder garage due to condensation (although my garage is probably big enough that it'd make little to no impact.)
 
2) How much air circulation do I need within the tent itself? Reading the other growing sites they all seem to have quite a few fans oscillating and blowing their 'plants' around, what is the benefit to this and does anyone know how necessary that is?
 
Other than listed above I have two 300W LED lights and plan on migrating my plants into the self watering buckets to avoid future overwatering issues, here's hoping to finally see some peppers!
 
 
Hey guested. 
 
You have quite a challenge ahead, and I am very interested in that :)
 
First thing I want to say is that "life will find a way". In the simplest terms, if you give the plants light, water, warmth and food they will grow. If you can give the plants a reasonable environment, they will produce.
 
As for your first question about the CO2 and air exchange. Yes you will need to exchange the air. But you may not have to do that actively. If you leave the vents on the tent open, that should allow the CO2 and O2 gasses to move into and out of the tent as needed. The problem then becomes keeping any humidity in the tent. If you add a humidifier, this humidity will eventually find its way into the garage or grow room. No way around this problem in an open system. And, if you think about it, not only are you trying humidifying the tent, you are also humidifying the entire garage... and perhaps humidifying the entire province of Saskatchewan.  Yes, you have a challenge ahead.
 
Most of the hot peppers that I grow do best when grown in a relatively humid environment. Do they need to be in a humid environment ??? I don't know for sure, but I would say that a minimum humidity should be 40-50 percent, and better yet 50+. Just my opinion which is not based on any study I have done.
 
Lights inside the tent can also add a lot of heat, so daytime heater may not be needed. That heat will have to be removed. If you use an active venting system such as a fan well, this will remove the heat, but also all of the humidity.
 
You have at least one thing going for you....your ambient temperature. Use this to your advantage. You may not have to suck the heat out directly via a fan. You could use an aluminum ducting material (heat conductive) that runs THROUGH the tent, and not into and out of it. Think of it as the sort of the reverse of a radiator in your car. In the car, the heat (hot water) in pumped into the radiator and the air flowing over and through the radiator cools the water. In your case, you could run the aluminum ducting into one side of the tent, run it back and forth across the top of the tent, and then feed out of the opposite side of the tent. The ducting does not feed air into the tent at any point....it just runs through the tent. Then you could place a fan outside of the tent that blow the super awesome ambient air through the ducting, sucking the heat out of the tent without taking any of the humidity with it ! This may not work with high wattage lamps though... but it works well for my 315W LEC with ambient in the low 70's in a 4x4.
 
If then you leave one or two of the tent vents open, it should still give an acceptable exchange of CO2 and O2 gas exchange that will make the plants happy. Just note that this does NOT eliminate the possibility of humidifying Saskatchewan... it does reduce it though since you are not venting the hot air directly.
 
You may need a heater during the night. I'd keep the temps in the mid 60's () at night. Humidity will get higher as the temps drop too, so you could get a humidifier that regulates humidity.
 
Number two is the internal fans in the tent. I am a total supporter of this. Circulating the air over the plants helps keep "hot spots" and "wet spots" to a minimum, and also helps keep the plants stems strong. Do this for sure !
 
Good luck !
 
Jeff
 
Thanks so much for that reply! I've been working on a lot of what you touched on!
 
I don't think excessive heat will be a problem while the lights are on, I've been test running it these last few days and even when the ambient garage temp. is ~72F the hottest the tent got up to was about 88F, so I'm guessing if garage temp falls to about 60ish that will knock a few more degrees off the high end of the tent temp. I think the lights might keep it at a really good temp during the day, then just a little supplemental heat when the lights are out from the heater. My two lights consume ~250W of power when on so a bit less than the setup you're using, I'm sure if I add another light I'll have overheating issues too and that duct idea is awesome and I will steal that when the time comes.
 
I could probably google this but if I remember back to high school I think plants only produce C02 during the night cycle, so I was thinking of just putting a small fan on a timer at night to blow air into the tent, I might be able to find something that could run the fan for say 10 minutes every hour, this would reduce the amount of air being exchanged out overall but still provide plenty of fresh air for the plants. I just wasn't sure about the necessity of this, but you confirmed what I was thinking. Maybe injecting 5-10 minutes of fresh air into the tent every hour day and night isn't a bad idea though, then just open another vent somewhere so it can passively exhaust through that.
 
Humidity will be a problem like you said. I was at the second hand store yesterday and grabbed a humidifier that looked brand new for $5 and when I got home and tried it I checked the price on amazon and it's $170+. Just a small humidifier but it doesn't have one of those crappy wicks it's ultrasonic and produces a very fine visible mist almost like a vape pen. It has 5% incremental humidity settings from 40-70% which is perfect. I've been playing around with it and it humidifies that tent fast! I think it, along with the standing water in the reservoirs if I move to self watering pots, should be able to keep the internal humidity in the range I want and allow me to adjust it to what I need. 
 
I'm not too worried about humidity escaping unless I go to an aggressive air exchange system, just from attempting to keep my house humidified and evenly heated over winter it seems like air doesn't really move around as much as you'd think it does unless you're forcing it to. If I get excessive humidity build up in the garage I'd have to scrap this project though but I don't expect it to be an issue.
 
Will definitely add an oscilating fan to my shopping list for inside the tent!
 
Thanks again for your post, I feel much better now and like I am on a path that might lead to potential success. I've never really grown peppers before (or any plant for that matter) but I'm anxious to see if this will work.
 
Hey guested... 
 
From what you wrote it seems that you've been thinking about this project... Good luck to you !!
 
For the moment I'd skip the fan to exchange the air.  Just leave a vent (not too small) open to allow the O2 and CO2 to exchange. If you can keep the temps in check and have good lighting... I'd start with that :)
 
Let me know how things progress... I am interested.
 
Jeff
 
 
 
Relative humidity doesn't have too much effect on chiles.
 
My closed grow room varies from 10% rh to 80% rh with no deleterious effects
 
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