wrote in message
ps.com...
It seems to me that cellulose has two drawbacks- 1) It is flammable. 2)
It is biodegradable and can support the growth of some micro-organisms.
The manufacturer could add biocides to limit this second issue, but the
underlying problem remains.
Polyurethane foam OTOH is inert to most micro-organisms but is
flammable. Flame retardants can be added but if the surrounding wood
supports the flame, it will still burn but with a lot of toxic smoke.
Could I suggest a small layer of fiberglass insulation on the attic
floor? It is not as an efficient insulator as the others, but from your
description of the temperature extremes you don't need that much. By
the same token, it will not cause as much overheating of the wiring and
will not by itself burst into flame if that were to happen.
If access for laying an insulation matt is problematic, I believe
fiberglass can be blown in the form of "chops" much like cellulose
insulation. Perhaps another poster has details on this.-Jitney

Cellulose is treated with flame retardant. That same flame retardant (boric
acid) is a fine insecticide.
I would be much more concerned about toxic smoke from drapes, upholstery and
carpeting.