I was in Colorado south of Colorado Springs before I came to Jersey. I grew in the house in front of windows. Very low humidity and very hard water. We didnt have air conditioning and I never had any trouble with my Paphs. I didnt have any trouble until I moved to New Jersey. In Colorado I grew all of my Paphs in clay pots and many of them were potted in straight Turface. In clay pots the Turface stayed damp for about a week. Incedently, the humidity is not much better in the house in NJ. Especially when the heat or air conditioning is on.
I think one thing that might make life a lot easier if you are hoping to have a greenhouse in Phoenix area would be to dig into the ground and have it partially sheltered in ground. Excavated soil could be placed on the sides. This could help moderate your temps a fair amount, I think
Evaporative cooling works well here for sure but has a tough time keeping up when it gets over 110 which is basically all of June/July/August. I have. water all on the back wall and a forced air swamp cooler on the side and still it gets to 90-95 in there. Have misters as well which helps also.
My first greenhouse here was 3 feet in the ground because I had an HOA so had to have it "below the wall". That probably helped a great deal but it is expensive to get dug out and retaining walls placed.