My terrarium is unfortunately in wait mode. It was shipped to me in June, and on delivery day the freight company called me to say it was broken.
It's been over 6 weeks since then. I'm still waiting for the replacement to ship. So here I sit with all the parts and my plans -- and plants-- but I'm not able to start playing with the settings. Which means that I don't yet know what the temps and humidity will be.
I've heard about the hacks people have made with wine coolers. Your link to the orchid karma website shows a really practical solution with the air conditioner hack. I also know of someone who has installed an evaporative cooler in his terrarium (his terrarium is big). The water for the cooler comes from a tank or directly from an RO system, so it is automated. He manages the temperature shifts by using fluorescent lights for light and heat by day and uses the evaporative cooler by night. He's not able to get an adequate temperature shift if he uses LEDs, so he sticks with fluorescents.
We've also talked about peltier coolers on this board but the consensus is that they won't get the job done.
Most of the solutions discussed so far are not going to work very elegantly in my sunroom. (By "elegantly" I meant aesthetically pleasing to my husband.) I am having a cabinet built to hold all of the tanks and equipment. The terrarium will sit on top with an upper canopy to hide the lights and sprinklers. It's supposed to look like a piece of furniture with none of the functional guts showing.The constraints I've created limit my options.
The reef cooler idea is intriguing. I will look into that!
Anyway, like you, I will just have to do some testing once it's set up to see what I'm dealing with. As winter moves in the best option might be to just crank the thermostat down in the sunroom before I go to bed at night. If I stumble across any bright ideas I will post them.