Ahhhhhh...hadn't even given greenhouses a thought! That must be how they do it!
I've thought about giving one a try inside in the a/c just to see if it can be done, just hadn't gotten around to finding and buying one I like. Way back when I was starting on this orchid addiction, and had no clue what I was doing, I bought one....looking back on it, I kept it alive for a good while before it died (only indoors though).
My friend Marisa (who got me started on all this, and the one I go to the Orchid Society meetings with) has just recently bought one to see if she could keep it alive indoors, which of course is what prompted me to attempt this as well, cause I'm a copy-cat!
I actually LIKE to have a few plants in the house, even with my big yard & garden...so maybe one of these days I'll find one I like and splurge....
You won't even let yours live in the house if it means they might stay alive? (Isn't that kind of the definition of "absolutely necessary"??)
