Zandor, thats a great calculator to get started with. I knew Id seen that around somewhere. This is all good, because I can stay with my original plan. The room will be entirely sealed except for the intake and exhaust. I will use some home made spring loaded trapdoors on the fans so that when they are not blowing they close up. That will really get it sealed.

I am doing about 100 plants at first, and Ill keep the room 10x10x8 until I decide to expand (I have a lot more room to work with but I figure small is good to start with cause you can control temp easier). Can A/C be used at the same time as CO2 to help control tempature? No issues with those messing with eachother? Do I still want my oscillating fans inside the room moving around the CO2 or do I want it fairly still? If I turn off all my intake and exhaust, that means turning off my air-cooled hoods as well (they are connected to the exhaust). So if I am keeping all fans off for a couple hours at the hottest part of the day...it might get pretty hot in there. Do I want to turn off my humidifier when the CO2 is released as well?

Zandor, any preferance on how to distribute the CO2? Will a fan on the floor bring it up into the room be sufficient? Or should I make a halo thing for the ceiling and let it fall? Or just release it on the ceiling? Does CO2 immediatly fall below air like a stone or is it a slower process? I could make pipes for it pretty easily (I am proficient in general construction).

It sounds like my 20 pound tanks will work fine for awhile, althoug if the generators only need a 5 gallon propane tank, thats available everywhere and super cheap. But it seems like heat would be an issue with them and I will be fighting the to hot battle, not the to cold battle.

As for watering. I was just going to hand water with a wand, as this operation is with a partner so generally if one of us are not around, the other is. With a planter box setup, I am expecting to water everyday (just not very much water) and I will use a res with the nutrients already mixed (like Tranoble has done).

Finally...I am making the assumption that for easy of controlling climate and for being as efficient as possible with the CO2, that I want the smallest room I can use for what I am doing?

Bah, lot of questions!