Cob: Cob insulation idea

[Myra Bonhage-Hale]

Hi, just wanted to tell you all about the Natural Home magazine Jan.Feb/2003
issue which  has an article in it "Bending the Grid".  pp. 52-58.  More
information on www.cityrepair.org.  It is an interesting article combining
the value of building community in urban neighborhoods with a cob type
structure as a focus.  I quote from the article,
"Cob, however, is a mediocre insulator with a low R-value per inch.  On cool
days, heat from within bleeds steadily outward.  To circuvent this, City
Repair designed a double shell; two six-inch walls of cob sepaated by eight
inches of insulating straw.  On each side of the straw is a wattle wall -
flexible sticks woven into a solid barrier-to hold back the cob.  This makes
for a thick wall, twenty two inches through.

The roof is eually innovative.  Above two-by-six rafters salvaged from
shipping palletes lies a polyvinyl chloride (PVC) membrane (PVC offers the
best protection against leaks buts it manufacture produces toxins.  Other
options include liquid asphalt or a rubber membrane.)  Atop this is a living
roof of sedum and other drought-tolerant plants which can withstand
Portland's often dry summers.  Rains trickles trough the greenery, down
bamboo gutteres, and into a set of sculptural ponds that hold water for the
garden.  This reduces pressure on both Portland's water supply and its
overtaxed storm-drain system.

The design is passive solar.  Ample south facing windows-all salvaged-"

The web site for Natural Home magazine is www.naturalhomemagazine.com.
These are very comitted  people, who supported West Virginia's Sustainable
Fair in 2001.  Back issues are also available.  Namaste.  Myra
----- Original Message -----
From: <lightearth at onebox.com>
To: <jwalker at magma.ca>; <coblist at deatech.com>
Sent: Wednesday, December 18, 2002 6:50 PM
Subject: RE: Re: Cob: Cob insulation idea


> We haven't had any problems plastering over and around the ends of wood as
they key in quite nicely...UNDERSTAND...we are NOT using cordwood and then
plastering over it, our 'Cob Scrap' is the ends of 2x4's and similar
construction waste (any non-treated kiln-dried lumber)set in the walls like
Cordwood so our goal is to plaster over the whole wall leaving an
earthen-plastered wall....
>
> the 2x4s etc. are to:
> a)use alot less Cob (and still make a incredibly strong wall- but fast!)
> b)tie the inner and outer walls together(we insulate between)
> c)provide a decent thermal break (good R according to Darel's calc.)
d)provide 'deadmen' in the wall for attachment points for screws
> e)reuse the horrendous amounts of cutoff lumber in the dumpsters around us
that go to the landfill
> f)be a non-toxic, very (already) dry-cordwood material that doesn't
require much processing....
>
> Rob Roy is right about not covering up the ends of natural wood and we
even started out our Cob Scrap projects with the idea of setting them to the
outside of the walls and then decided that they'd only look good if we
arranged them in patterns, which we might still do, but thought that this
took away from the speed of buiding...you COULD arrange the 2X4's into a
pattern in places, leaving them exposed, and even paint the ends for a
sunburst effect or something - worth a try!
>
>
> Marlin
>
>
>
> <snip>
> Hi Marlin, how is plaster doing over the wood ends? I asked Rob Roy of the
> Earthwood Building school how plaster would work over the cordwood (with
cob
> mortar) and this was his reply: dont know about clay plasters over
cordwood.
> People do it all the time with ordinary cement plasters, with good
results.
> I think that it is worth a try. Worst case is that the plaster cracks and
> falls off. The endgrain of the wood might rob the moisture rapidly from
the
> clay plaster and the rapid drying might be detrimental. You could be the
> first to do it! (I guess not-jen)  But don't cover it all. The main thing
> about cordwood masonry is that it is beautiful. Rob
>
> Just wonderin'
> Jen
>
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