PipeDown wrote:

Thanks everyone. It looks like solid core is the most practical solution
from an installation standpoint. I just need to study the price a little
more to see if it is really worthwhile (and find just the right material
locally). I may insulate under one bedroom at first to see if it makes any
difference. I might be able to get a good price from a packing materials
company for foam core like material.

Another Idea that came to me was to string up nylon mesh (or similar) and
fill it with packing popcorn as I get it leftover from shipments at work.
Filling may be gradual but might cost nothing.

Tyvek instead of mesh/wire. The rigid is an easier installation, the
peanuts are free. I wouldn't want to be the one stuffing peanuts into
something over my head while I was lying on my back.

R