Now that's a lot of wood!

Ambient RH looks pretty good. (I could only find Austin RH data on-line http://www.txstate.edu/freemanranch/...limatology.pdf , as I can't access NOAA's detailed data because I'm not in the US.) Once your door is in, you can probably season the wood in the room by just opening that outside window at night!

What's your in-house RH like? I'm guessing that will drive how big a humidifier you will need.

I am assuming that there is no air exchange other than the door opening/closing, you are not planning on smoking in there (?), and your cooling is from the house interior via those big windows. You may have to point an oscillating fan (from inside the humidor) at the windows to reduce the windows' insulating efficiency and prevent condensation forming on the windows. Or maybe not, I'm just guessing from looking at the pics. (Glass is not a good insulator, but the thin layer of dead air up against the glass is. That's why double-glazed windows work.)

I'd be tempted to start with something like this one, which maxes at 65%RH: http://www.kaz.com/kaz/store/product...a8b4afac8ee4d/ (Honeywell HCM-6012I) The price of consumer units is so low compared to meant-for-cigars units ...

You can always plumb in an RO system somewhere where you can use it as a source of drinking/cooking water as well, and then later modify the reservoir for constant refilling.

Anyhow, just a suggestion. No doubt Bob Staebell can set you up with what you need without a lot of guessing/extra work/experimentation/etc. A lot of times it is worth the extra cost to pay for the "voice of experience."

Good luck!