[Cob] Slipstraw R values and sneaky techniques? Plumbing past a stone foundation?

[Mike]

Hi folks!

I'm in Chapel Hill, NC.  I've a number of friends who have
builtgorgeous structures from cob, but given it does spend some time
belowfreezing, they can be a challenge to keep warm in winter.  Some
havedone modified straw-bale/cob houses (like north walls in bale).
I'mbuilding a 12x12 workshop in my backyard, and was leaning
towardcob... til I realized it'd actually be a 9x9 interior space.
Now I'mleaning toward a slightly less "green" approach: stick
construction,but slipstraw (aka straw-cob) infill for insulation, with
lime plasterexterior and earth plaster interior.  On 6" stud walls,
that'd give mecloser to 11x11 interior space.  I'm curious though -
what's the Rvalue (approximate, of course) of packed straw?  I've seen
anywherefrom .25-1 for cob (more mass than insulation).  And bales
(properlyplastered so minimal air flow) I've seen 2.7 R/inch if
strawperpendicular to heat flow, 2.4 if parallel.  So I would guess
packed,nonstructural slipstraw to be closer to the 2.7 mark?  That'd
put 6"studs around 16.2 and 8" studs at 21.6 R.

Another thought I had, to save on lumber costs, would be to have
theouter frame (sill plate, side members, top plate) be 8",
butsupporting members be 6" or 2x4s - and just fill the whole wall
withthicker slipstraw.  If you placed the inner framing
members(structurally sufficient for a little workshop - thickness is
just tokeep the walls thicker) every other stud on the inside or
outside ofthe bottom 2x8 you could still use forms for the packing.

Thoughts?

Secondly, I'm nearly done the drystack of the stone foundation -though
I think I'm going to unstack it and do a bit of concrete/soilmix for
infill to try to keep mice and water permeation to a minimum.I'm
plumbing the structure, and am a bit stumped at how to run thevent
stack for the little sink, toilet, and shower.  My best guess isto use
an inside wall to get the height I need on the stack and then"wiggle"
over into the wall bay once I'm past the height in
theextending-above-grade stone foundation.  When I plumbed my house
Ijust popped past the block foundation into the crawlspace, but in
thiscase I'll have an earthen floor... and a small loft that'll keep
mefrom riding the inside wall all the way up.

Double thoughts?

Thanks, cob aficionados!

Mike

-- 
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"The greatest achievement is selflessness.
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The greatest quality is seeking to serve others.
The greatest precept is continual awareness.
The greatest medicine is the emptiness of everything.
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The greatest patience is humility.
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to the elevation of mankind. With respect to luxuries and comforts,
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