cool! literally! i had a similar set up (on a much much much smaller scale) growing up...dad built me a "bank" barn...the top was his wood working shop and the basement which opened up on the back side of a hill was where i kept my steers and lambs...didnt have the ac...just a few fans and sullivans misters and it stayed a cool 60 degrees...nice and dark too...and then an exercise lot that ran down the hill out the back...but that was way back in the day, lol...i think there is something to those basement barns though...doesnt seem to take much to keep them cool...
cant wait to see more!