Disclaimer: Before you all start slamming me, understand this. I have no idea how effective this really is, because its not my setup.
Since nobody has mentioned this idea at least in this thread, I thought I would bring up the idea and see what you all thought.
I was recently evaluating a co2 system in my friend's garden, and he is running a lot of fresh air in and out of the room, on opposite ends. 14" duct fan for exhaust and two more 10" intake duct fans.
I asked him of course, wouldnt it be a waste to have a co2 tank/regulator in a room with that much air exchange? wouldn't the exhaust fan would remove it all quickly?
He tells me, that in a sealed room, it would cost a fortune to run a Mini split AC, plus Dehumidifier, etc. Plus the amout of co2 you would need to inject in a sealed room to keep it at 12-1500ppm is massive, and far from cost effective for most people.
Since co2 is heavier than air, he has several lines coming from the regulator, each ending over the tops of the plants, so as the co2 drops down to the floor, it falls through the plant canopy.
Keeping some of your wall mount fans low(to the ground), and the intake/exhaust on opposite ends of the room, the whole environment is constantly swirling the air within the room, allowing the plants to take up more of the co2 before it is exhausted, instead of it sitting near the floor after initially falling, where the plants cant absorb it.
Essentially it is a co2 supplemnt, or booster system, to add extra co2 to the fresh air that is constantly coming in. Fresh outside air, has enough rich co2 to make most peoples efforts futile, as far as cost/benefit, like most people have already brought up.
According to my friend, he goes though way less co2 than a sealed room would take, and tells me he sees massive leaf growth/width, vs the same room without co2 supplement, which equals more photosynthesis, (the ability to use large amounts of light, and therefore the ability to grow more plant matter, considerably faster. Flowers, leaves, thicker stems, etc. Leaves are natures solar panels, and have one main purpose. To convert/transfer light energy into usable plant energy through a process known as photosynthesis. A lot of people complain about overly leafy bud, but more leaves = more ability to grow buds.
I would love to hear all your opinions on this type of setup, as it sounds promising, and I might even want to try it out myself one of these days! The initial cost is probably 1/10th that of a sealed room setup. Pretty sure its just a tank and regulator, and some tubing. I dont think he even uses a co2 controller or even a ppm reader. He has been doing this for so long, he's got it all fine tuned to the point where he doesnt need those things. He knows exactly how to tune the regulator at for his setup. For us, it might take some experimentation without these instruments, to get this right, as every setup is different, but this guy obviously benefits from it, or he wouldn't be using it. This is not his first rodeo. Sounds like a pretty cheap effective use of a co2 tank, since there is plenty of free co2 just outside your room! This is just a simple booster, and does not require a super controlled environment that requires very expensive equipment to function at all.
Good luck to all in your co2 efforts!