Hi Jess,
Fiberglass is outside my area of conservation expertise, but I was able to ask my colleagues for some suggestions on the topic. I learned that fiberglass is a trade name and the generic term is “glass reinforced plastic” or “GRP”, which may change your general search results.
You can read about the conservation of several outdoor GRP sculptures at the Getty here: http://www.getty.edu/conservation/publications_resources/newsletters/27_2/temporary_art.html
Most of the research I found pertains to outdoor GRP, and I did not find anything relating to insulation material. I have a few more people to follow-up with, so hopefully I can get some more specific information for you. I would also recommend posting the Conservation Dist List.
Best,
Maggie