GBlist: Superinsulation for Vaulted Roof

[barblinn <barblinn@uswest.net>]

I am looking for suggestions for insulation system for the roof which
provides an equivalent to
R-45 insulation I am hoping for from the strawbale walls.  The great
room will be vaulted ceiling
with exposed trusses.  The roof material is corrugated metal or standing
seam.
I am expecting to use rigid insulation, so not too disimilar to SIP's,
except constructed on site.

I am concerned about using rigid insulation because of the toxic fumes
if burned.  This house is
in a high fire risk area in northern California.  I would also like to
use the most sustainable
material for the insulation without creating an outrageously thick roof.

Any body use anything lately that is also easy to work with?
Any help is much appreciated.

Barbara Linn



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