Cob gleanings from the SB archives (LONG)

[M J Epko]

Cob & cob-related posts from the CREST archives of the SB newsgroup:

*

From: "Steve J. Sibert" <sibert at lynx.dsaco.dsai.com>
Date: Mon, 7 Aug 1995 08:48:02 -0600
Subject: "Cob" Construction

Hi Folks,

This was posted in the alt.archetecture.alternative newsgroup. It seemed
somewhat applicible to the discussions on this list. It was posted in reply
to a question like, "What is `Cob` Construction?".

Steve Sibert

The process is very simple, you can start experimenting with it now.
It reached its peak use in Germany I think. (It is still widely used
there and has been for hundreds of years). Here's how to do it.

1. Get some straw and put it in a pile.
2. Mix clay to the consistency of a milk shake with water.
3. Pour the "milk shake" over the straw, tossing with rakes or
pitchforks until just lightly coating the straw.
4. Place in between boards and tamp with a 2x4 or 4x4. (about 3-4 ft.
long)
5. Move the boards up immediately and stuff some more.
6. Allow the wall to dry. (Time varies by climate)
7. Plaster inside and out with soft plaster
8. Use a water resistant plaster on the outside.

The clay is not too critical, anything from 40-50% clay soil all the way
up to all clay will work (at least in my experiments). You don't need to
add sand. Save the sand for the plaster.

Mostly post and beam construction is used and boards on each side of the
posts make up the "form" to stuff the staw-clay into. Walls can be 6
inches to 18 inches or more, thick walls take longer to dry.

That's about it.

I like this approach. It is superior to staw-bale. The only problem is
that roofs are still expensive. I am working on a system that allows the
straw-clay system to make domes and build the roof at the same time from
the same material. Then you can really reduce the cost of housing. Just
ferrocement in inner and outer shells and you have a really strong
structure!

Steve J. Sibert

*

Date: Tue, 08 Aug 1995 15:11:15 +1300
From: aalcorn at arch.vuw.ac.nz (Andrew Alcorn)
Subject: Re: "Cob" Construction

"Cob" as far as I am aware, correct me if I'm wrong, originated in England
where the word originally refered to the handful of mix (soil, water,
chopped straw. horsehair, gravel, whathaveyou) that was placed on the wall
as a `cob'. The wall was built up in this way and then trimmed back with
some sort of blade to give a flat surface which was then plastered. The
finished wall is then a `cob' wall. The English have certainly been using
this method for hundreds of years.

        [snip the how-to instructions requoted from the previous message]

This describes a method which is known here as the Light Earth Method (LEM)

>I like this approach. It is superior to staw-bale.

Superior in what ways? Insulation? Speed? Cost? Thermal mass?

Andrew Alcorn

*

From: Debiibarra at aol.com
Date: Wed, 25 Oct 1995 03:18:05 -0400
Subject: R value of cob

Information I recieved from a cob building workshop is that the R value of
cob is about 1 for every inch, the walls are usually 12-18 inches thick, so
R12-R18 for the wall. This is about half of the R-per-inch of a straw bale
wall, but SB walls are usually 24 inches thick, with an approx. value of R55.
The thing is, cob walls provide thermal mass, which SB walls do not
have(except in the plaster coats). This thermal mass stores heat, but also it
has a heat transfer rate of about 1 inch per hour, so for a thick wall, by
the time the wall discharges its heat stored up during the day and warm
inside air starts to travel thru the wall, it's getting warm outside again,
and this stops, and the wall will get recharged again. It is good to remember
that R values are not the only thermal characteristic we should be concerned
with. Some interseting buildings I've seen combine SB and cob, with highly
insulative SB used for the north wall, and cob for the other walls. Cob takes
longer to build with, but is very well suited to curves and roundness... 

Debi

*

From: BALEHEAD at delphi.com
Date: Thu, 26 Oct 1995 10:57:52 -0400 (EDT)
Subject: R value of cob

> The thing is, cob walls provide thermal mass, which SB walls do not
> have(except in the plaster coats).

The interesting question here is...how much mass do you need? I have heard it 
said that two inches of mass is all that really gets used in a normal
building. Although the idea that the sun's radiant heat travels through the
wall and keeps your toes warm at night is an appealing notion, the reality is
much more complex, involving such factors and volume space vs exterior wall
area; interior/exterior temperature differential; angle of sun; cloudy vs.
sunny days; interior temperature and air circulation within the building; and
what side of the bed you sleep on. 

> It is good to remember
> that R values are not the only thermal characteristic we should be concerned
> with. 

We had a thread not long ago about incorporating the radiant temperature of
the walls into the thermal characteristics of a building. Walls cooler than
the air feel cold, like they're sucking heat, and people turn up the
thermostat to compensate. Warmer surfaces (such as radient floors) tend to
lead to lower thermostat settings. A high-mass wall, such as cob or rammed
earth, is almost always cooler than the air temperature and can be experienced 
as uncomfortable, chilly and cold. 

> Some interseting buildings I've seen combine SB and cob, with highly
> insulative SB used for the north wall, and cob for the other walls. Cob takes
> longer to build with, but is very well suited to curves and roundness... 

I like this approach: let the sun in through windows (not walls) and trap it
with mass. Put your mass on the walls and places where the thermal transfer
will be efficient (like the floor in front of a window). The bale walls,
being well insulated, stay close to the ambient air temperature; and cob
benches, interior walls, etc. provide a thermal flywheel. 

Having built a rammed earth house which last winter's occupant described as
the coldest building she'd ever lived in, I'm sensitive to the subject. The
house had adaquate insulation and a good furnace, but lots of cold exterior
walls. Have you ever visited Great Britian? 

This week, the straw bale walls of the Real Goods retail store are being
blasted with three inches of pise'--a mixture of cement and earth applied in
the manner, and with the equipment, of gunnite. This method, because it
requires only one pass by the labor force (rather then three-coat stucco); is
somewhat cheaper than stucco, and shows potential where designs call for high
mass but climate or conditions (like earthquakes), make earth 
walls difficult or undesirable. [If Ross Burkhart is lurking in cyberspace,
he can tell us how it went this week]. 

John Swearingen

*

From: SIMON RANDELL <SARSR at cardiff.ac.uk>
Date: Thu, 26 Oct 1995 12:11:38 GMT
Subject: Re: The thermal insulation of cobs in mud

On Tue, 24 Oct 1995, Robert W. Tom wrote:
> Just to make it CRYSTAL clear, there's a fellow in WWW-land who makes a claim
> that mud-slurry coated straw has an R-value exceeding 3 per inch. I posted
> this claim (with a disclaimer) to the list and a challenge to you to set the
> record straight. It seems your silence has led many to believe that the
> claim is true, judging from posts that have appeared lately.

Joe says: IMHO: mud-slurry coated straw does not have an R-Value 
exceeding 3 per inch. My best testing showed an R-value of 2.3 per inch 
and 2.9 per inch for bales with the grain of the straw and against the 
grain of the straw respectively. Density, moisture and materials are 
also factors. I'd assume that mud would reduce the air content of the 
material and thus reduce the insulating value.

JoE

(For anybody interested)

I recently conducted a thermal heat transfert and thermography test on a cob
cottage here in the UK (we have 40,000 structures in the SW). The result:

U'Value - 1.0 W/m2degC
density - 1860 kg/m3
test duration - 29 days 

Density obviously had a huge effect and so did the heating source. 
Moisture content unobtainable due to metals in the mix giving 
inaccurate reading. Anyway, not bad for 170 year old building!

*

From: jstanley at gate.net (John A. Stanley)
Subject: Re: The thermal insulation of cobs in mud
Date: Fri, 27 Oct 1995 07:21:53 -0400

In article <Pine.NXT.3.91.951026143119.8626Y-100000 at fenris.space.ualberta.ca>,
Sherwood Botsford <sherwood at space.ualberta.ca> wrote:
> 
> > On Tue, 24 Oct 1995, Robert W. Tom wrote:
> > >
> > > Just to make it CRYSTAL clear, there's a fellow in WWW-land who
> > > makes a claim that mud-slurry coated straw has an R-value exceeding
> > > 3 per inch. I posted this claim (with a disclaimer) to the list and
> > > a challenge to you to set the record straight. It seems your silence
> > > has led many to believe that the claim is true, judging from posts
> > > that have appeared lately.
> > >
> >
> > Joe says: IMHO: mud-slurry coated straw does not have an R-Value
> > exceeding 3 per inch. My best testing showed an R-value of 2.3 per
> > inch and 2.9 per inch for bales with the grain of the straw and
> > against the grain of the straw respectively. Density, moisture and
> > materials are also factors. I'd assume that mud would reduce the air
> > content of the material and thus reduce the insulating value.
> >
> 
> But Joe, the clay coated straw is no longer in bales, and so may have a
> lower density/cubic foot, implying a larger amount of air per cubic
> foot. From other descriptions, I've gotten the impression that the clay
> to straw ratio is low enough that the straw only looks dirty, not clay
> coloured.

1. The ratio of clay to straw can be varied to achieve greater
or less thermal mass.

2. The density depends on how much the mix is tamped down. When
used as attic insulation the mix isn't tamped at all.

John A. Stanley

*

     Subject: Re: Straw-clay vs. cob (no SB here ... ) 
     From: "Ann V. Edminster" <74200.746 at compuserve.com> 
     Date: 01 Feb 96 03:17:15 EST 

Toby, and anybody else who's interested:

Not to pick nits, but your last post implied that straw-clay and cob are one and
the same. They're not. A primer follows.

Straw-clay is a mixture of mostly *straw* with some clay, that is packed between
forms which are then removed as the lifts of the wall are built up -- a little
like rammed earth in terms of the process; not in terms of the product. The
forms can be removed almost as soon as the compacting is done. Each lift is a
foot or two high; the wall thickness (as usually done in the U.S.) is typically
a few inches. Straw-clay panels are created between vertical supports (2x studs,
e.g.).

Cob is a mixture of mostly *clay* with some straw, that is pressed, kneaded,
tamped, etc. into place, usually without forms, in fairly thin layers (4" to 12"
per day, depending on ambient temperature, humidity, wall thickness, etc.). The
walls are quite thick (a foot or two, tapering to somewhat less at the top).

Ann V. Edminster

*

     Subject: Re: Cob goblin 
     From: Shannon Dealy <dealy at deatech.com> 
     Date: Thu, 1 Feb 1996 22:21:09 -0800 (PST) 

I don't know the answers to all of your questions, and my knowledge is 
limited to a few conversations and a tour with the people of the Cob 
Cottage Company, but here goes:

> Sam says:
> 
> This has gotten me interested.  I am putting up a post and beam goat barn
this 
> summer and have been thinking about what to sheath or infill the thing with.  
> 
> Do you use any wooden rods or other ties to keep the cob connected to the 
> building? 
> 
In the buildings I've seen, the Cob is the building, with wood embedded 
in the Cob to allow attachment of Doors, Windows, etc.

> If cob is 1 foot thick and the post is 7 inches do folks just cover the posts 
> with cob?
> 
see above

> No sand is mixed in?
> 
It depends on your soil composition as to what if anything you need to 
mix in (I heard Ianto Evan's of Cob Cottage refer to one person's soil as 
"Ready-Mix")

> Is mixing done like making bricks: a pit with clay, straw, and water,
mixed by 
> barefeet?
> 
I don't recall the exact mixing method, but essentially this is correct.

> What about a cobblestone and cob mix?
> 
I'm not sure what you mean here, if you are talking about embedding stone 
in the Cob to reduce the Cob required, I don't think this would be a good 
idea, since this would tend to disrupt the matrix.  Think of cob as a 
really crude form of fiber glass, the straw is the fiber, and the 
clay/soil is the resin.

> What about cracking and the joint between timber and cob?  I am especially 
> thinking about the opening up of the crack as the timber completely dries (no 
> kiln dried stuff for me!)
> 
This is handled, but I'm not sure how.

> Got any good references?
> 
Cob Cottage Company            (A non-profit corporation)
Box 123
Cottage Grove, Oregon 97424
(541)942-2005 FAX (541)942-3021

The put out a 60 page book of collected articles on Cob construction (about 
$10 - $12), they also give 1 week workshops on Cob construction (last 
years workshops were scattered over western North America from Mexico to 
B.C. Canada.

Hope all this helps.  I'm planning on attending one of their workshops 
this year, so I'll probably have more info in about 6 months.

Shannon

*

     Subject: Re: Straw-clay vs. cob (no SB here ... ) 
     From: Strawnet at aol.com 
     Date: Fri, 2 Feb 1996 03:17:19 -0500 

WRT (with regard to) straw and clay building systems:
I like to think about the spectrum of straw and clay building methods.  On
one end is straw bale (almost entirely straw), then there is light
straw/clay, perhaps a heavier straw/clay, cob. adobe (with a small amount of
straw) and probably rammed earth, sand bags, etc. with just clay or dirt with
no straw.

I don't like to think of these things as any one being inherently better than
any of the others - without talking about them in context.  It isn't straw
bale is better than cob or rammed earth is better than straw/clay.  It
depends on where, what, by and for whom, when, how, etc. and I LOVE the idea
of hybrid structures that use what is appropriate where it is appropriate.
 We have a spectrum of properties as well as materials and we should think
about them this way too - thermal mass, insulation, sound insulation,
breathability, resistance to moisture, sculptural ease, degree of effort and
difficulty of execution, and so on.  This makes the selection a conscious
process, not a contest.  As Pliny Fisk said in Austin, Texas a couple of
weeks ago, "We should be seeing much more hybridization than we seem to have
right now."  I fully concur.  

David Eisenberg

*

     Subject: Re: Cob gobbin' (no SB) 
     From: "Ann V. Edminster" <74200.746 at compuserve.com> 
     Date: 02 Feb 96 10:08:04 EST 

Yes, Sam, that was a lot of questioning you did! I'll do my best to answer ... 

>   I am putting up a post and beam goat barn this summer and 
>   have been thinking about what to sheath or infill the thing with.

In general (though I may be misinformed; others are far more expert than I), cob
is its own structural system, therefore questions about embedding posts, etc.,
don't arise. However, to do what you are proposing seems entirely feasible.

>  Do you use any wooden rods or other ties to keep the cob connected to the 
>  building? 

Yes, I would tie the posts to the cob somehow. One method we have used to embed
things like lintels is called "porcupining" -- pounding a whole lot of nails
(the more crooked the better) into the wooden element and then cobbing around it
to create a really good mechanical bond.

>  If cob is 1 foot thick and the post is 7 inches do folks just cover the posts
>  with cob?

You could bury the posts, either wholly or partially. My inclination would be to
expose them, probably on the interior; that way, if they did rot out, you could
replace them.

>  No sand is mixed in?
>  Is mixing done like making bricks: a pit with clay, straw, 
>  and water, mixed by barefeet?

Depending on the soil type, varying proportions of sand may be mixed in. Several
mixing methods have been used: feet, tossing in tarps, in concrete mixers ... 

>  What about a cobblestone and cob mix?

Cobblestone and cob mixed how?

>  What about cracking and the joint between timber and cob?

Ensuring that there is enough straw (organic rebar) in the mix is crucial to its
crack-resistance. Controlling the rate of drying is another factor (I mentioned
relatively thin layers ... that's why). And again, a good mechanical bond
between dissimilar materials will keep joint problems to a minimum.

>  Got any good references?

VERY good:

Cob Cottage Company
Ianto Evans, Linda Smiley, and Michael Smith
Box 123
Cottage Grove, OR 97424
541-942-2005 (MWF 10-1 best)

CCC have lots of literature, a newsletter, workshops, etc. (all over the country
and abroad). I encourage you to contact them.

Ann V. Edminster

*

     Subject: Re: rubber stucco & stucco tie-in 
     From: NAT1VESUN at aol.com 
     Date: Fri, 2 Feb 1996 14:45:26 -0500 

        [snip]

As DE mentioned: Hybrids are what really makes sense.  I whole heartedly
agree.

My 2 cents:
Use s.b. on walls/ Soil Sandbags and Adobe for garden walls and benches/  Cob
adds freeform possibilities and creative sculpture/ Light-clay can fill in
areas between posts/ Rammed Earth for trombe walls/ Pumice-Crete for poured
in place walls that can be earth-bermed/ High performance glazing systems for
passive solar gain/ Sustainable Energy Harvesting systems for Energy needs/
Super Efficient Appliances

        [snip]

Chris Prelitz (Typin' in the rain) in So. Cal.

*

     Subject: Re: Mixing Cob 
     From: NAT1VESUN at aol.com 
     Date: Fri, 2 Feb 1996 14:45:33 -0500 

> Question:  Is mixing done like making bricks: a pit with clay, straw, and
water, mixed by  barefeet?

>Answer:  I don't recall the exact mixing method, but essentially this is
correct.

Ann.. remember all of those DElerious, dancing, barefoot lads and lassies
doing a jig-in- the-cob at the Natural building Colloquim?

An 8x8 or 10 x10 blue plastic tarp was the mixing surface of choice.

They danced away for a bit with mud-pies oozing between thier toes,
accompanied by Live music of course. (With Motts playing the double-sided
washboard.)

Then 2 people grab the tarp in the corners and do a strong side-to-side
 motion to mix up the mud and clay...More dancing..more tarp swaying and
voila..COB!

The tarp helps in dragging the cob to where its needed.

Hope that helps.

Chris  

*

     Subject: Rockstarred (same brush) 
     From: Strawnet at aol.com 
     Date: Mon, 5 Feb 1996 02:55:16 -0500 

        [snip]

- somewhat serious section - 
What is most important is to recognize that, as others have and will continue
to point out, there is no single appropriate building material, method,
system or design.  Straw bale construction is not the best choice in every
location or climate, nor is stone, frame, concrete, adobe, cob, straw/clay,
steel, earthship, space frame, etc, etc, etc.  Stone buildings have killed
many people, as have adobe and other earthen structures, as have wood
buildings, steel buildings and so on.  Straw bale hasn't yet, but it's
probably just there haven't been very many chances yet. Does this mean we
should never use these materials? Of course not.  I love stone, I love adobe,
cob, straw/clay, all of them - WHEN and WHERE they are appropriate.  That is
VERY climate, local resource, culture, skill, and design specific.  

I like dry stacked stone foundations for straw bale buildings if the above
conditions are right for doing it.  I love stone floors and fireplaces and
thermal mass walls (inside an insulating envelope).  I doubt Sherwood is
going to love a stone thermal mass house where he lives unless it's
superinsulated on the outside - I could be wrong but I doubt it.

Remember - All generalizations are false (except this one of course).

- end serious section -

That sulphur now.  I can't zinc of anything else.

Rockin' DEsert Dave Eisenberg
My rhetoric usually getstoned down (felled 's par for me)

*

     Subject: Moisture, Breathing walls, etc. again 
     From: Strawnet at aol.com 
     Date: Wed, 14 Feb 1996 03:16:04 -0500 

        [snip]

I have said (amid a chorus of others) before that cement stucco is probably
not the ideal wall finish for bale walls.  In New Mexico, many mud
(unstabilized) adobe buildings were destroyed by the act of "preserving" them
with cement stucco.  I am more convinced than ever that cement stucco is not
very good at transpiring moisture out of bale walls or any other construction
type for that matter.  I am more drawn to lime and sand plaster and adobe
plasters, stabilized or not, for their known compatibilty with materials like
straw and mud.  This is the traditional plaster for earthen construction, the
old straw-clay and cob buildings and timber frame buildings.  

        [snip]

David Eisenberg

*

     Subject: moisture issues-not lime per se 
     From: Strawnet at aol.com 
     Date: Thu, 14 Mar 1996 02:42:34 -0500 

In talking about the stucco/moisture issue here, I am talking about a piece
of information I mentioned some time back from Bob Platts in Canada (Linda
Chapman's engineer and formerly Luis Gagne's engineer among many other
things) who called and left a message for me about the fact that in the
Pacific Northwest there were more and more reports of moisture related
problems in buildings with cement stucco finishes.  He  said this was not
straw bale buildings, but all building types and he was just pointing out
that cement stucco may actually turn out to be problematic for moist climates
on any substrate.

I have said many times that I agree with the French Canadians and the French
bale builders that cement stucco is not the ideal finish for bale walls.
 Brittle and hard, subject to permanent cracking (on ANY substrate), not
especially breathable (particularly in the thicknesses that often result from
attempts to straighten out irregularities in walls with the stucco), and the
potential that eventually it will get painted with a non-breathing paint -
after the cracks have been caulked and look awful.  This is why they prefer
lime and sand plasters - softer, somewhat self-healing, more breathable, and
they reveal underlying moisture problems more readily.

I also mentioned the significant body of information on the damage that
cement stucco has done to mud adobe buildings in New Mexico and elsewhere
when it was used to "preserve" the buildings and resulted in destroying the
underlying adobe by creating a condensation surface within the wall, creating
a greater moisture barrier than the traditional mud plasters, and hid the
underlying deterioration from view.  I refered to Ed Crocker's work in
restoring adobe missions in New Mexico in the short piece I wrote for issue
#8 of The Last Straw (Fall 94) and suggested that there are lessons to be
learned here.

Lime and sand or mud plasters are better at revealing underlying moisture
problems, less likely to create them in the first place.  Lime plasters have
been used for centuries on straw/clay and cob structures and I have not heard
or read of problems associated with the lime destroying the straw in these
systems.  That doesn't mean that it might not be a problem, just that I
haven't heard anyone discuss it.

And finally, we come back to the fact that the majority of the historical
straw bale structures have cement stucco finishes and they stand without
obvious problems as a result of it.  Again, I'm not positive that there might
not be a problem with lime and straw, I'm just saying if there is it hasn't
revealed itself in an obvious way.

David Eisenberg

*

     Subject: Re: SB vs. cob building 
     From: Jorg Ostrowski <ash at freenet.calgary.ab.ca> 
     Date: Thu, 25 Apr 1996 07:49:25 -0600 (MDT) 

Nancy: For cold climates, SB would be far superior from an insulation
point of view. There would be too much thermal bridging through cob
construction. Haliburton is prety cold. It would be simpler and faster
construction as well. But SB construction is very different
in Canada than in the US because of the rigors of climate.

Jorg Ostrowski

*

     Subject: cob & SB building 
     From: "Ann V. Edminster" <74200.746 at compuserve.com> 
     Date: Thu, 25 Apr 1996 12:22:15 -0400 

Nancy,

Homes combining cob and strawbale construction methods are in the planning
stages, but I am not aware of any yet completed. There are homes in the
southwest U.S. that combine adobe and strawbale, with the adobe as thermal
mass (TM) on the building interior, and strawbale for the building
envelope. That climate is quite different from yours, but the strategy is
the same -- store some of the building's heat in the interior TM for
release at night, and protect the TM from the exterior cold.

Empirical evidence also seems to defy the conventional wisdom that cob's TM
would be a liability as an exterior wall material in cold climates, because
it has long been in use in chilly, gray parts of northern Europe, with
reportedly high levels of thermal comfort. All materials exist somewhere on
a spectrum from insulative to thermally massive; earthen materials are
generally considered to be on the thermally massive end of the scale.
However, cob mixes vary substantially, and those with greater proportions
of straw in them are more insulative than those with less; the other
ingredients will also affect the cob's insulating capacity. My intuition is
that, in the global scheme of things, cob is somewhere on the middle of the
scale and may therefore offer a balance of performance in different
seasons. Friends who live in cob homes in central Oregon (a very gray
place, where TM is normally thought to be a thermal liability) find them
remarkably comfortable year-round.

Last fall a cob-strawbale dome, designed by Matts Myhrman, was built at the
Black Range Lodge in western New Mexico (in the high desert, where it
snows). Bill Hunt lived in the dome all winter long -- for a while without
a door -- and found it quite comfortable. The cob made an ideal
mortar/chinking material to fill the wedge-shaped spaces between bales
created by the three-dimensional curved semi-spheroidal shape.

Cob Cottage Company: P.O. Box 123, Cottage Grove, OR 97424; 541-942-2005
(MWF 10-1 best).
The Last Straw: 1037 East Linden, Tucson, AZ 85719; 520-622-6896.

Hope this helps --

Ann V. Edminster

*

     Subject: re: Cob Building + re: Wytong Block ??? 
     From: be417 at freenet.carleton.ca (Robert W. Tom) 
     Date: Sun, 28 Apr 1996 12:40:28 -0400 

on Thu Apr 25 09:11:21 1996
wildrose at accent.net (Nancy Lugsdin) wrote:
re: cob building

>    ... cob and SB... anyone have experience with combining the
>    two forms?  ... building in Haliburton [ North-Central
     Southern Ontario Canada, approx 45 deg NL ]

No fair eh ?  How are people like Sherwood and I going to get a
word in if you don't say :

" Anyone have any *THOUGHTS* and/or experience WRT combining the
two forms ?"  

The intention *was* to exclude loonies like us ? Oh. I see.
Hmmph.

As Ann and Jorg (who are not loony) have indicated, cob will have
minimal insulative value (about R-1 per inch) and will be
beneficial as thermal mass (TM) for moderating temperature
swings, with a slight penalty in terms of additional wall
thickness and approx. 30% lower thermal mass capabiltiy
(guesstimate) as compared to 2" of a cementitious material like
stucco.

Notwithstanding Ann's optimistic offerings :

ave> Friends who live in cob homes in central Oregon ... find
ave> them remarkably comfortable year-round.

ave> ...a cob-strawbale dome ...in western New Mexico (in the
ave> high desert, where it snows)...lived in the dome all winter
ave> long -- for a while without a door -- and found it quite
ave> comfortable.

(No door ???)  One wonders how much auxilliary heat was added to
achieve the "comfortable" temperatures. Even a refrigerator
carton is comfortable in winter, if you have agood down sleeping
bag and keep a fire going all of the time when not in the bag.

The coldest location in New Mexico that I could find information
for, was for Raton (6417 degree-days per year). This is
comparable to Penticton, British Columbia, Canada which
experiences a climate of 6410 degree-days per year. 

Haliburtonians go to Penticton during their winter vacation to
escape the cold don't they ?  For a Haliburtonian (~8750 DD/yr)
6417 dd/yr would be a heat wave.  Besides, no door in Haliburton
would be suicide- by- blackfly and mosquito. No bull.

For Haliburton, a Cob/SB Hybrid offers interesting possibilities.

It would be wise to take advantage of SB's high thermal
resistivity (R = 2.1 to 2.9 per inch according to JoE) to help
reduce the heat-load requirement of the building volume.

Roof snow loads will be a big concern. Rather than resort to a
timber frame/SB infill, it seems reasonable that an interior cob
wall, utilized for its thermal mass capability, could do double
duty in a roof-load-sharing arrangement with the SB thermal wall.
Perhaps a vaulted cob ceiling with SB over too ?

As mentioned in earlier posts, the cob wall could be used to
carry the utilities (triple duty ?), thus eliminating the
necessity of compromising the integrity of any air/vapour barrier
asembly which would permit (this one's for bridgman at aol.com, who
I want to call "Mel" for some reason) MOISTURE LADEN AIR to
EXFILTRATE through the penetrations INTO the SB. For "Mel's" sake 
I shan't get into a discussion as to why that would be a " very
bad thing". (the exfiltration that is, not Mel. BTW, who's Mel ?)

I don't think that there's any advantage (in Haliburton) to using
cob on the outside unless you consider having to provide extra
foundation width to accomModate the 6+ inches of cob as an
advantage. 

It would have to be plastered over anyway to be weather -durable. 
In fact, it may even prove to be a liability in that it would
tend to inhibit the ability of the SB to transpire any
accumulated moisture... and that would be very b-a-a-a-d.

        [snip]

Rob  Tom

*

     Subject: SB & cob?/SB + RE in 11,000DD/year climate/KISS 
     From: Jorg Ostrowski <ash at freenet.calgary.ab.ca> 
     Date: Sun, 28 Apr 1996 21:17:36 -0600 (MDT) 

Rob/Nancy: Having design/built with rammed earth interior walls and SB
exterior walls (with shallow footings & rubble trenches) in 11,000 DD/year
climate, it is a challenge from both a design and construction point of view
to accommodate solid structural systems that don't move on the interior
and flexible wall systems (initially) on the exterior that do move. Therefore,
based on experience, the simpler it is, the cheaper it will be.

        [snip]

Jorg Ostrowski

*

     Subject: B.C. Load Bearing Permit 
     From: habibg at trianon.worldtel.com (Habib John Gonzalez) 
     Date: Tue, 30 Apr 1996 20:10:39 -0700 

        [snip]

        Re: Cob and SB-Ianto Evans of the Cob Cottage Company gave a talk
last Friday in Nelson, BC. When asked about cob construction in cold
climates he said, "If I lived in Winnipeg, only the south wall of my house
would be cob (for solar gain) and the other three would be straw bale."

All the best, 

Habib