If you’re growing in a dedicated flower room that is ~8’x8′ or larger there are good reasons for supplementing CO2. Every indoor commercial grow I have toured supplements CO2 into their grow rooms. CO2 Supplementation increases growth by up to 35% and the plants love it.
There are some considerations to be made when building a supplemented CO2 grow room. You need to seal your room so that CO2 does not escape. Since your room is sealed you can no longer rely on the exhaust fan controlling temperature. Instead you need an Air Conditioner to control the climate. Having an air conditioner in your room is great for DWC since you can drop night time temps to keep reservoir temps low (helping prevent root rot).
As one of my friends once said, trying to control the climate in an un-sealed grow room is like driving down the highway with your windows down wondering why the AC is not working.
This room is a dedicated flower room, so if you are in the planning stages be sure to either add an additional veg room/tent or make sure you have access to a healthy supply of clones.
Materials Needed:
- CO2 Tank (I use 20lb Aluminum tanks)
- CO2 Regulator & Solenoid
- Inkbird CO2 Controller (Alternatively get the CO2Meter brand Controller)
- 1/4″ Black distribution line (typically included with regulator)
- CO2 Alarm (outside room for safety)
- Pulse Pro – CO2, Temp, PPFD and VPD monitoring
- Use code ‘GROWDOCTOR’ for $25 off
- Air Conditioner (Window Unit or ideally a Mini Split)
- Get at least 2 BTU per Watt of LED lighting
- Dehumidifier
- Caulk (I went through 9 tubes)
- Poly Seaming Tape (aka TUCT tape)
- Weatherstripping gasket (sides and top of door)
- Under Door Seal
- Frosted Window Stickers
- GreatStuff Expanding Foam – Pest Blocker (for large gaps)
Optional Materials:
Tools Needed:
- Caulking Gun
- Drill
- Staple Gun
- TUCT Tape
- N95 Mask
Overview
Step 1: Seal The CO2 Grow Room
Frosted Windows
For privacy reasons I always install frosted glass on any windows. This window will have an AC on one side and styrofoam insulation on the other side but it still looks better from the outside if you add window frosting.
The window frosting comes in large rolls that stick onto the window. It can be purchased super cheap on amazon.
Cut to size and use a spray water bottle to apply to the window. There is no adhesive used, the suction holds it to the window for a clean quick install.
Sealing Grow Room Gaps
There is a reason that expanding foam is sold under the trade name “the great stuff”. It is pretty great and they have a pest blocking version that is formulated with ingredients that help keep bugs and small rodents from eating their way through the foam. This stuff is amazing for sealing holes up to 5″ in diameter.
For smaller gaps use Alex+ caulk or a silicone to seal.
Sealing a Grow Room Door
When sealing a door divide it into two parts. (1) The sides/top and (2) the bottom of the door. Typically the side/top seals go on the frame while the bottom seal goes directly on the door.
(1) I used Weatherstripping gasket for the sides and top. Clean the surface with a mild detergent before applying for max adhesion.
(2) For the bottom I found this excellent under door seal infused with Diamotaceous earth. Each of the fins that fit tightly against the threshold is coated with diatomaceous earth, a natural, completely non-toxic substance made up of the fossilized shells of tiny, aquatic diatoms. These abrasive particles form scratches on the exoskeletons of any bugs that manage to squeeze under the door seal and this damage kills them.
I had to shave off about 1/8″ from my door for a perfect fit. I think home depot is the only place that sells this stuff, I could not find it on amazon, though there are many non Diatomaceous versions if you don’t have an old bug-filled house as I do.
That is about it. Once you have your door and any cracks sealed you are ready to install your AC unit.
Step 2: Install Air Conditioning and optional exhaust
When choosing an Air Conditioner it is recommended that you use a minimum of 2 BTU’s per watt of Full Spectrum LED lighting. I picked up an 8,000 BTU Toshiba Air conditioner to use with my 2,500 Watt grow room as it is always better to have extra cooling capacity so your AC does not have to work as hard. Mini splits are ideal because they gaurantee no bugs can get in through the AC (the indoor and outdoor components are separate). The problem for me is a 1 ton mini/split in Canada costs upwards of $2500 and you need a professional to install it (they won’t even sell them to the public here). A window unit in the same cooling capacity can be had for $400. Which brings us to our next task:
How to Bug Proof a Window AC
Today’s Window AC units are designed well, but they still are not completely bug proof. The best way to ensure bugs don’t get in to your grow room is to take the AC apart and carefully seal any gaps and line the bottom with double sided tape that’s covered with diatomaceous earth a natural pest blocker that shreds the soft bodies of aphids and mites. This may seem like overkill but bug proofing a window AC turns essentially turns it into a cheap affordable mini split.
Apply the diatomaceous earth in any areas where bugs may want to crawl towards the front of the AC. Use the two sided tape to make strips (a bucket helps). Wear an N95 mask while working with this stuff, it can cause respiratory irritation. Don’t use any diatomaceous earth in the front portion of the AC. You don’t want the stuff getting blown into you grow room.
Fill any gaps that may allow bugs to crawl into the indoor portion of the AC (front). The Toshiba AC I bought was sealed fairly well, but there were still a few big gaps around the circuit board that required caulking.
Congrats you have sealed your window AC so that it can function more like a bug-proof Mini Split, at a fraction of the cost.
Installing an Air Conditioner in a Grow Room
If you are using a window air conditioner and not a mini-split you should take care to fully seal the AC into the window to prevent bugs from entering through the sides.
Start by building a wooden frame for the AC to sit on. This will give you something to apply caulking to.
Insulate the window using styrofoam. A jigsaw will give you a cleaner cut than trying to use a knife.
Cut a piece of plywood to fit over the window, with a cutout for the AC. This will allow you to seal the AC with a seam of tape as a final line of defence. Caulk the plywood to the wall.
Step 3: Install CO2 Regulator and Controller
Setup your 20lb tank in a corner of your CO2 grow room. Use a wrench to attach the regulator to the tank. Don’t forget to use the washer on the seal between the tank and regulator. This is what is known as the high-pressure side, so be sure to get a tight seal between the regulator and the tank to prevent leaks.
Open the tank with the solenoid unplugged. There should be no hissing noise, if there is you have a leak and need to tighten the tank. Plug the solenoid directly into the wall to calibrate the regulator. Plugging the solenoid in will open the valve. Adjust the regulator so that the little ball floats up just slightly. You want the flow to be very slow so that you don’t overshoot your target ppm.
Install the Inkbird CO2 Controller (or whichever controller you went with) and place the CO2 sensor at canopy height. The inkbird does not have auto-shutoff at night but there is a simple solution to this, simply plug the controller into the same power bar that controls your lights. The controller should only run when your lights are on (plants don’t use CO2 at night).
Plug your CO2 regulator into ‘WORK1″ on the Inkbird CO2 controller. Set the sv to your target ppm. I recommend between 800-1200. pv is your present value of CO2 (in ppm) and is a good thing to compare with your other CO2 sensors.
Step 4: Pierce and Run CO2 line
Use a small pin to pierce the distribution line. The CO2 line should be run along the top of the room as CO2 is heavier than air. Note that CO2 is miscible with air, as long as you have a good air circulation via oscillating fans the co2 will spread throughout the room. This is sometimes called “raining CO2” on the plants. The line that came with my regulator was a bit short so I added some extra 1/4″ OD water line for even distribution in the grow room.
Step 5: Install CO2 Monitor and Alarm
In my setup I am using the Pulse Pro to monitor levels inside of the room. Outside of the room I have a CO2 alarm setup for safety. It alerts above 1000ppm. I also have a homebrewing keezer in my basement so the potential for CO2 leaks certainly does exist. Having a device like this with an audible alarm give me peace of mind when it comes to safety. CO2 is not toxic like CO but it can cause problems as it displaces air. Be sure to get a CO2 monitor and not a CO monitor as the latter is much more common.
Step 6: Install Pulse Pro
The Pulse Pro is a beast of a platform, which I will be reviewing in more detail in a dedicated article. The Pro monitors VPD, PPFD (light) and CO2… the driving forces of photosynthesis and thus the most important metrics for any grower to monitor.
The app makes things easy by giving you insights into how to tune in your grow room. Setup the Pulse Pro as per the directions provided in the manual to get it on your wifi. I am part of the Pusle Pro Staff team (that gives feedback and guidance on new devices) so use the link above (or discount code GROWDOCTOR) for $25 off.
The Pro is very accurate. In the screenshot above you can see the effect on CO2 levels just by being in the room and breathing while doing some defoliation and transplanting. Proof that it pays to hang out with your ladies (after changing into clean bug/PM free clothing!).
Step 7: (optional) Install Exhaust Fan
Excessive CO2 during the night cycle can cause yellowing of the leaves. I run a quick 1 minute exhaust at the end of the night cycle to purge the room and drop temps. Having an exhaust fan is also excellent to have for venting the room if you do ozone sterilization between grows. The exhaust fan is controlled by a smart plug so that I can exhaust whenever I want -remotely- or setup repeating exhaust schedules (e.g. one minute at lights off).
If you are installing an exhaust fan you should also install a backdraft damper to keep air from leaking in/out of the room.
Increase Temperatures with CO2 Supplementation
Supplementing your room with CO2 allows you to increase room temperatures beyond normal ranges. You can run daytime temps up to 10-15 degrees F warmer than without CO2. You do still need to tune in your environment for your given cultivar. As a starting point my suggestion is to run night temps at 65F (to reduce risk of root rot) and then boost daytime temps to 75F during veg and 80F during flower when supplementing CO2.
Enjoy your new CO2 grow room gains and as always happy growing!
UPDATE: I received an alert (from my Pulse Pro) that my flower room from had a light leak. It turns out the styrofoam used for the air vent lets light through. This turned out to be an issue because I run my night cycle during the day to conserve electricity.
This was easily fixed with a quick coat of black spray paint. Since I already had plants in here having an exhaust fan came in handy for venting the spray paint fumes.
