Nice! Any chance you can send me some of that insulation? 
Not if I want to keep my job.
The open market price for the amount of insulation I'll be using in this chamber is probably $1500-$2000.
A couple of questions/comments- Do you have air returns for each of the ferment chambers? You'll need a return to get enough airflow to control the temperatures.
Good point. I may or may not have considered that, but I didn't think of it while I was making the drawing.
It may be easier to have air flow from ferment chamber 1 to chamber 2, rather than all the way from the cold box. You can still control them independently, but fermenter #2 will have to be the same temp or warmer than #1.
That was my original design, but then I realized I would have to plan ahead to make sure I had the higher temp fermenter in chamber 1. Planning ahead isn't my strong suit.
Also, I like the idea of being able to cold crash either fermenter independently.
You may want to add louvers or some other way to block the airflow, so that when you are running the heater you aren't heating up the cold box.If you can get all the insulation you want, make the walls 3 1/2 inches- the width of a 2 x 4.
Yes on the louvers and probably yes on the 2x4 construction. My original design used 2" EPS foam as the structural members (the insulation i'm using is in granular form, so it isn't self supporting). 2x4s have about 5 times the thermal conductivity of the EPS, but if I'm upping the wall thickness from 2" to 3.5" that probably wouldn't matter since the overall heat load would be lower, even with the high conductivity wood structure.
Are you making it long and narrow to fit in a certain spot? If you can make it more square, you'll have less wall per the same area. Also, you should make it a bit wider than 2 cornies so you'll still have good airflow when it's full. Can you increase it to 24" wide?
I am kind of space limited, but I haven't done all the measurements yet. I don't want it to be too cramped in there, but i also don't want it taking up too much space.
You should have no problem keeping it as cold as you want. I'd definitely use it for serving. I'm running a 5000 BTU window AC on my cold box, which is a 48" cube. The insulation is probably not as good as what you can get with the foam (it's framed 2x4s with regular roll fiberglass), and judging by the condensation it has some air leaks. I keep it set at 40F now, but it will go into the 20s if I crank it up. I'm using the AC's thermostat, so it did just that while I was dialing it in, tweaking the set screw on the thermostat to find the right temperature range.
Well, that's good to know. I was alittle worried about the cooling load, but from what you're saying it seems very doable.
So the idea is that the first chamber on the left is the cold storage/lagering chamber, it will be temp controlled at ~35-40 (pretty much as low as I can get it) and be able to store at least 20 cornies. I'm also thinking if I can get the whole thing down into the 30's, I can use the cold chamber for serving as well. The two fermentation chambers will be connected to the cold chamber and the temperatures can be controlled independently by using fans to force the cold air to the ferment chamber. I also have heating elements in each of the fermentation chambers. My basement can get below 50 in the winter, so I want the option to be able to heat the chambers. I also want to be able to get each of the fermentation chambers just as cold as the main chamber so I can cold crash in the fermenter. Of course, the key to this system is outstanding insulation, thermal breaks in the design and keeping everything perfectly sealed. Otherwise, I won't be able to get the temp down low enough. I have access to unlimited, free, high performance insulation, so this thing is going to be crazy insulated. The insulation I'm going to use is R8/inch (the best foam you can get at your local building supply store is R6.5/inch) and I'll probably go with at least 2" thickness, maybe up to 3.5".So, that's that. 
