You'll have to adjust your minimum temp and light levels for your most tender plants. Which one(s) might that be? Maybe the majesty palm? Not sure. If so, I would say minimum temp of 55 degrees. All the plants you listed could have different ways of overwintering and varying light levels, temps, etc. Some go dormant, others need to keep growing. That's a long list and too hard to address in one message.

Doubt you'd need to add humidity. Is this a separate building from your home? Might be expensive to heat. Is it insulated? Yes, adding skylights would be a big plus.

I've never wintered Majestys, but would assume they need warmth and lots of light. Otherwise, throw them out and start over next year with new plants.

You'll have to do some research on which are your most tender plants and the minimum temp they will take.

I guess I was trying to create a pseudo-greenhouse environment. The pool house is separate from the main house. It is insulated and has skylights in the kitchen area. It also has one full wall of windows/sliding doors which is situated below an awning. It receives quite a bit of light via the skylights once the oak trees loose their leaves.

I figured the ferns (esp Australian tree fern) would require some humidity. The majesty palms are, more or less, an afterthought. I only paid $5 each but have around 10 or so and would like to save them if I can.

I guess I figured it would be easier than hauling every plant to the basement. I probably need to do as you suggested and figure the individual requirements of each plant. I'm new to the whole "overwintering" thing. I usually just throw a few potted plants in the house and pull them out in the spring. However, my collection has grown a LOT since moving to this house and I just don't have the room. Maybe I'll just have to try the pool house idea and learn by trial and error :)

no better way to learn than just get after it. The majesty palms are prone to mites for some reason so pot them up, give them as much light as possible, mist them several times each week, keep a fan on them for air circulation, minimum temps in the lower 50's , cut back on watering and you are good to overwinter.

I've been checking into supplemental lighting, humidifiers and heaters. I think I can create a pretty decent environment for all my tropicals with what I have found. But I hadn't considered circulation - guess I'll just keep the ceiling fan on out there. Fortunately, our winters only last a few months. Thanks for your suggestions. We'll see how it goes