Has anyone installed a central air system in the 20x30 1 1/2 story plan? We live in Alabama and will need conditioned air to use the cabin in the summer. I am considering putting the cabin on a slab so that would eliminate the ability to run ducting under the house. What are my other options if I don't do a central system?
Have you looked into mini split systems? It's kind of like a wall unit, but the compressor is separate like a central unit. I've heard the Mitsubishi Mr. Slim is the one to get. Just Google 'mini split air conditioning' for lots of info. Another possibility is to use open trusses for your floor joists. There's usually enough room for ductwork in them, and the ductwork will be in conditioned space, rather than a hot attic.
The unit can go in the attic space with the compressor at ground level. I know of several who have done this. Any HVAC contractor can give you the details.
No reason the ducts can not go into a slab (actually under it) It is a matter of getting the correct ducting (round corrugated pipe) I've been in the HVAC business for over 15 years and have put hundreds of duct systems into slab homes. The only hard part would be the loft area you would need a chase to run pipes up to it/