[GBlist] Venting cathedral ceiling/roof insulated with cellulose?

[Whitney Burgess & Tristan Kelley <raven@tetontel.com>]

Greetings! from a guy who needs to make up his mind on whether or not to
vent the cathedral ceiling/roof of a strawbale in-filled house that will
be insulated with dense-packed cellulose.  I've found conflicting
information regarding the necessity of venting when dealing with
cellulose.  One theory is that no additional vapor barrier or venting is
necessary, due to the fact that there is no "bulk air movement" through
the cellulose due to it's high density, thus very little moist air to
condense with in the roof?  Others warn of mold and other nasty problems
associated with not venting (soffit vent to ridge vent) the dense-packed
cellulose roof?  The "crew" is finishing the fascia (thus decision time)
and since flipping a coin seemed a little too arbitrary a
decision-making technique, I am requesting any insight you fine folks on
the strawbale and greenbuilding listserv might have into my ventilation
dilemma!

Details:
roof rafters are 11 7/8inch  I-Joists
sheetrock on underside of rafters
5/8 CDX sheathing on roof deck
10 in 12 roof pitch
26 gauge corrugated metal roofing
cold weather, snow country environment
location: SE Idaho, USA

Thanks!
Tristan




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