Walk-in cooler build thread

[TreetopVT]

Background:
I have an unconditioned space, completely sealed and underground. Temperatures hold pretty steady in the 60's except during the summer months when it can climb into the low 70's. It has worked great for fermenting my carboys, but I am graduating to conicals and I want to brew year round with accurate temperature control.

I've decided to section off an unused area of this space to build a walk-in cooler that will let me roll in fermenters, age kegs, store grain, and cellar my beer/wine. I am going to build it out of 2x3's and high-density foam board. The total floor space should be about 30sqft with a 6' high ceiling. I am planning on cooling it with a mechanical window air conditioner (5050btu).

Now some questions:

• I doubt I will want to drop below 50F in this room. Would insulation with an R10 value be enough, or should I aim for R20?
• The "parent" room already has a dehumidifier so I am not terribly worried about condensation/humility. Do I still need a vapor barrier?
• I want to control the temperature of all my fermentors from some micro-controller, most likely a variant on the brew-pi. If I run lengths of Cat-5 to a couple of low-voltage boxes, would I then be able to use them to connect to my existing phono-plug ended temp probes? The total run from the low-volt box to the controller location would be about 12'. I am concerned that the signal would degrade over that distance/wiresize.
• Ideas for lighting? I have a florescent shop light that I was initially thinking about using, but now I am considering maybe some led fixtures, namely where I plan to store the wine/beer.
  
  Thanks for reading and I'll do my best to document this as I go along with pictures and lessons learned!

 

[TreetopVT]

I'm usually bad about the "before pictures". Here is what it used to look like and the space cleaned and ready to begin the build.

 

[TreetopVT]

Here is the framing completed along with wiring pulled. I decided to do a single cat 5e wire run for each sensor I anticipate needing. In one area of the cooler I will have a low volt plate with 3 RJ12 ports available. 1 of these ports will be for the cooler temperature so my air-conditioner controller can read the internal temperature. The other two will be used to connect thermocouples to my various fermenters. I then ran two more cat5 cables to another wall in the cooler with the same thought. This will give me more flexibility when I determine how best to use the space. Next to each cat5 box I have a single gang box with one run of 3-wire romex. This will allow each outlet socket to be used independently. This will correspond to the sensor wire and be controlled by my controller outside the cooler.

Up next, the fun job of sizing and fitting in all this foam board!