The back house needs everything: from insulation to interior walls, flooring electrical, plumbing, kitchen, bathroom etc.

Starts with setting up plastic containment around mold infected area, negative air HEPA filters, drywall and insulation removal, literally scrubbing studs with wire brushes, and treating with chemicals.

Then we had to replace areas of framing on interior and rebuild the window framing plus repair the aged window, but you might need to consider new window as well based on how many on that wall. then drywall and any other infrastructure that needs to be done on that wall: electric plumbing, etc. that affected wall had plumbing so new code dictated double wall with insulation on outer most wall which added additional cost. termite damage went as high as the roof truss and I needed to replace a beam, but luckily above the bottom beam was the only affected area.

Move the insulation away from the bases and check to see if they are on an interior wall.

Try spray foam insulation in your ceiling.

Check if you have bare pipes in the attic, if you do, get them wrapped with pipe insulation. 

Has Owens corning insulation was added to the ceiling and a sound deafening highend cork floor to keep the place peaceful.

If you're paying for heat, it matters that the windows are replacement, roof is insulated, etc.

And what was year built / insulation situation?

This is a long term buy and hold for me and I just had central AC installed so was looking for something that held some type of insulation value but was also concerned about hurricane protection as I don't want to be running around to all of my properties in the future putting up plywood.I wont be paying for heat but the bottom line is these windows will have to be replaced sooner or later.