Now, that is a tough insulation situation. Since you live in Florida, which is quite humid, you are going to need to be really careful to ensure that you do NOT trap humidity with insulation, which could lead to serious moisture damage and/or mold.
As full disclosure, I live in a pretty dry climate, so I will be relying on building science principles, rather than direct experience, with this answer.
I'm thinking the best option would be to insulate from the outside by using rigid foam board.
- If you can access the roof, you could potentially use OSB faced rigid foam board beneath roofing material.
- You could also potentially use rigid foam board (seam taped) along the entire exterior of the house underneath whatever siding choice you select.
This will not be inexpensive, and you should check with www.bpi.org to see if there are any BPI Accredited Professionals in your area that can take a direct look at your home.
Another option could be "drill and fill" cellulose insulation; however, given the moist climate, and the requirement for patching/painting afterward, I'm not thinking this would be a cost-effective or low-risk option.
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Read "I have a 2,000 sq. ft. mobile home that I'd like to transform to a self-sustaining structure with solar power. Help!" a Q&A answered by Sergio Grado.