Crawl Space Grow Successful! I need thoughts to make it better!

So everyone said don‘t grow in a crawl space. However, I wanted to setup a second tent and that is the only place that I had room.

This is what I did. I setup a 3x3x6 grow tent on its side, bought a 4 foot LED (link below) put a heated tile floor in for the winter, and a can 33 filter and fan in.

I had 6 plants in the tent and put netting at a diagonal. I trained the plants into the netting. I used high quality seeds and Fox Farm Dirty Dozen Fertilizer with adjusted PH. This setup yielded over a half pound of pretty good bud.

I wanted to push on and make my bud better! I thought that the Co2 might be low in the crawl space so I bought an AutoPilot APC8200 Co2 Controller. It said my co2 was between 300-400 PPM. I bought a regulator and a 20 pound Co2 tank and started dosing Co2. I realized that the Co2 was escaping so I shut the vents in the tent. This made the humidity sky rocket.

My solution to the high humidity was to run a duct fan for 10 minutes every hour to vent the tent to the Crawl Space and release the humidity. This however only brought the humidity to about 85% which is still way too high (I was probably way too high as well).

So here is my question. How do I keep Co2 high and humidity low In a small crawl space grow???

This is what I am thinking but would love to get more options. I could get a second smaller tent such as a short stack or mother keeper and put a dehumidifier in it. Then I would make it a closed loop ventilation system with the grow tent And flexible ducting. This way I could circulate the air through both tents without having the dehumidifier use valuable grow space. I am worried about the dry air blowing on the plants but at least I can direct it with the flexible ducting.

Does anybody have any advise or easier options for me?

This is my light. MARS HYDRO SP 3000 LED Grow Light 4x3ft Converage Compatible with 960Pcs Samsung LM301B Leds& MeanWell Driver& Daisy Chain Dimmable Full Spectrum Indoor Grow Light Lamp UV IR Veg Bloom Commercial Grow
link to light:


Thanks in advance!

You can use a ducted dehumidifier. They generally aren't cheap and are for much larger spaces. Nothing small that will fit inside the tent is going to fix that much humidity imo, and if you exhaust well you might as well say bye bye to your CO2 and the expense of a controller etc. I'm not an experienced indoor grower so maybe someone else can point you a cheaper route.

I have an old ducted AC unit that is also a dehumidifier. I haven’t run it in years and I’m worried about how much energy that will consume. Thank you for your ideas!

The best thing you can do here to increase your production weight and quality is forget about co2 and run a proper vented space and concentrate on your plant health and proper nutrition.
I promise you will gain more from keeping those plants fed the correct amount and keeping them happy than you will from adding co2.

Ditch the C02,, is it not possible to run a closed loop exchanging air into and from the house. Unless you you have no climate control at all in your house I'm betting the air from the house is your best bet. I would just install some floor registers. Pull air from the coolest dryest part of the house and vent near your central air intake if you have one.

Do you have ducting already present in the crawl space you could maybe use?

I don’t have ducting in the crawl space. The house has window units. The crawl space is sealed pretty tight and I don’t really want to make many holes in the house.

I'm not sure what to tell you, your in a crawl space they aren't know for being dry.

You need to be able to move air in and out of the tent that doesn't go into the crawl space. Venting humidity into the crawl space then pulling it back into the tent isn't likely going to drop humidity very much unless your climate is very dry.

Air from the living space is the best option as it's already somewhat treated by your window AC. If that is not an option you need to vent to and and pull air from the outside.

The option of the dehuey in another tent on a closed loop is going to heat up the tent even more as dehuey to pull that much moisture put off a good bit of heat.

If your humidity and temps were manageable with the way you had it set up then run it that way 300-400 ppm of c02 is workable, 80 % humidity is not.

I still vote for finding the least intrusives spot to cut holes to one of the rooms with a window AC and pull and exhaust to this room. Since it's a living space it will have slightly higher c02.

I know cutting holes sucks but it's quite often inevitable when growing.

So the crawl space is only 300 square feet and I do run a dehumidifier down there anyway. What if I just leave the vent fan on and still slowly dose Co2? Im not worried about going through Co2. It is easy for me to get. I’m thinking if I leave the c02 running I can slightly increase levels of the whole area? If I put the c02 sensor outside the tent I could set it to shut off relatively low like 500 PPM.

Is that a crazy idea? Implications?

Thank you so much for your help Apachen!

Can you install a moisture barrier on the floor on top of the dirt since it's only 300 Sq ft.

This idea of using c02 in the whole space might be workable, not sure how affordable. Since it's a relatively small space you could line the floors, ceiling and walls with poly (can use cheaper I stead of panda film since it's for moisture not reflection). Then you can use your portable ac and dehuey outside of the tent and you won't lose as much c02.

It would be a lot of work but could well be worth it if you put in the work. Seems like a lot of work for one smaller tent but if you got it nice enough down there you could always add some more tents.

The walls have an insulated plastic poly covering already. I had it professionally insulated and sealed to keep the floors above it warm. When I get heavy rain the far corner gets wet but the dehumidifier dries it right out with the help of the sump

ReefingR said:

The walls have an insulated plastic poly covering already. I had it professionally insulated and sealed to keep the floors above it warm. When I get heavy rain the far corner gets wet but the dehumidifier dries it right out with the help of the sump

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Awe sounds nicer than most crawl spaces. That is good. I guess you can try the tank and see how long it last. I couldn't imagine it would last long with the exhaust running. But I guess it depends on how well the crawl space is sealed up.

I think that’s the plan. I just moved 3 plants down there to flower.

Thanks again!

Why don't you just cut a vent hole to the outside and vent it all outside. No need to worry about the smell then. It will solve your humidity problem too!