Cob Re: fibrous cement

[M J Epko]

Gordon,

	Thanks for presenting your reasoned responses to my skepticism about some
of the claims surrounding FC. I appreciate the ingenuity and development
that's going into the technique, and am looking forward to the next issue
of EQ. I finally took the time this evening to get away from this evil
time-sucking computer to sit down with and really thoroughly read your
first issue.

	Philosophically, I'm in full support of the ideas behind FC, absolutely.
Owner-build, mortgageless, (evidently) high-performance, (certainly)
low-tech, beautiful (to my eyes). The idea of using a waste product is
appealing... my primary emphasis is always on the best compromise of
recycled/repurposed, cheap, safe, least-toxic (micro & macro), durable, and
climate-appropriate. The answer's not always cob, not always strawbale, and
it isn't always going to be FC, as you're comfortable pointing out, which I
appreciate.

	My aim is to try to determine where and when FC is and is not appropriate.
I seemed to be seeing a lot of hype and unanswered questions in the last
several weeks about the technique, and no discussion of its potential
downsides and problems. Strawbale struck me the same way when I first
started investigating it; I felt as though I wasn't being shown the whole
picture. This casts no aspersion your way, since you're also learning about
FC - though you know much more about it than I do or probably ever will.
I'm hoping that you'll continue to enlighten me and the others interested
in this technique.

	I'm posting this response to the cob and strawbale lists as well, where
there's been questions about FC; for that reason, I'm going to be very
clear about the discussions I'll be raising - not because I don't think
that you haven't already thought about these things, or that you don't
understand them. It's going to a wider audience, some of whom may not know
what I'm talking about. (And why should they? I so rarely do myself, and
this may be no exception.)

	My misquoting of the figure on the front cover was a significant error. I
said it was $7 a square foot... it in fact says 75 cents, as you pointed
out, and then verified that the figure represents the cost of a minimal
shell. In your response, you said, "We are talking about materials only...
face it -- what do you get for 75 cents a square foot? No foundation, no
windows (Sean uses glass bottles), an exterior coating (on the house of
Sean's that appeared on the EQ front cover) that may or may not work..."
'Nuff said. I was thinking of a finished minimalist home with the niceties
we've come to consider essential like plumbing, electricity, possibly a
heat plant, etc - not a minimalist rain shelter. I confused the use of the
word "house" with my use of the word "home." My misunderstanding.

	For the sake of comparison, the R value of FC is quoted to be 2.8 per
inch. Fiberglass batts are 3 per inch (dry, and properly installed). Some
blown-cellulose insulations are rated at just over 3 per inch (same
caveats). Strawbale is commonly given 2.4 per inch with the grain, and 3
against it... though lower figures have been determined in some tests. Cob
is cited by some sources to be less than 1 per inch, about the same value
hardwoods and dry uncompacted dirt are given; that value has been contested
as being too low for cob, but I'm not so sure. Straw-clay, surprisingly, is
given a similar number to cob by some research... though an American source
that I haven't been able to track down (however, I just received several
good leads offlist, as though intuited - thanks!) gives it almost 3 per
inch. In light of the many variables in numbers that exist for so many
materials, I'd be interested in knowing how the R value of FC was
determined, what the testing conditions were, the mix and density and
moisture content of the material tested, etc.

	Of course, that doesn't take mass-effect into account. FC is quoted as
being "a substance that has a high insulating value and a high thermal
mass, all in one package. There is no other building material that can make
this claim." Other building materials coming to mind that likely would have
a viable shot at the banner would be the lightweight air-entrained
fiber-plus-binder products like Faswall, Rastra, etc., and possibly a
couple of the manufactured strawboard products.

	On the owner-builder front so close to my heart, straw-clay (such as the
Steens have been working with in block form, and LaPorte as an infill) can
make that claim, depending on whose numbers a person chooses to believe...
and it's been used for many hundreds of years in Germany. (In fact,
according to Frank Andresen, a German straw-clay restoration expert,
ready-mix bags [just add water and straw] are sold in Germany for that
purpose.) Since straw is stated to be an acceptable substitute for paper to
supply the fiber in FC (the straw won't likely "soak up" the cement like
paper), and cement/sand/clay all have lousy R-Values (cement is the worst
in terms of thermal resistance), I'm guessing that the results are figured
to be similar.

	That said, since FC is stated to be 3/4 sand & cement and 1/4 paper by
weight, and 80% air by volume - whereas straw-clay is about the same,
except with the binder/filler and fiber ratios reversed and then some, and
probably less air - one might think that straw-clay is more on the
insulative side than FC... despite the numbers I mentioned earlier
indicating that it's more massive than insulative. So who knows, really.

	Every wall material has both mass value and insulation value; FC is
ostensibly striking a balance between the two. In the same paragraph, the
quote continues "... a fibrous cement wall will take all day to warm up,
and all day to cool down." That's exactly what adobe and cob proponents
have been saying for centuries, and strawbale proponents for a hundred
years... hardly a "revolutionary" statement.

	I run into another quandary there in that statement, and not just with FC:
typically, depending on density and other characteristics, diurnal
temperature swings affect only the first couple inches of a given mass, as
I understand it - even in the case of direct insolation. Perhaps that was
the intended meaning: that when it's hot during the day, the wall will heat
up to a certain depth from the sun on one side and warmed interior of the
structure on the other, to a depth of maybe an inch or so on either side
(since FC is so highly thermally-resistant), but not all the way through
during the course of a day... then when it's cold at night, it'll radiate
that heat back into the room and to the outside. All materials do that to
different degrees. The quandary I run into is in my understanding of how
mass walls work. I could be wrong; I often am. Correcting me will help
everybody, so if I've presented something incorrectly, somebody speak up:

	Over time (how much time depends on the material... we might assume that a
12" FC wall of R-33.6 might take as much as several days before it reaches
core-temperature stability), the effects of diurnal temperature
fluctuations on uninsulated mass walls (which is what a FC wall is when
we're talking about it in this capacity... K-Value, the measure of thermal
'transmissivity', and its inverse sibling R-Value, the measure of thermal
resistivity, are not mutually exclusive: they co-exist, and can't be turned
on and off) in generally-cold or generally-hot climates can be disastrous
to comfort. If a diurnal thermal flywheel effect is invoked in a place
where the mean summer temperature is 90F (which is not determined by
averaging the daily high and daily low temperatures, but by charting
hour-by-hour or even minute-by-minute temperatures... in other words, a low
of 70F at night and a high of 100F during the day is an average of 85F; but
if it's 100F for three hours during the day, and 70F for a half-hour at
night, they don't cancel each other out), the wall will naturally want to
moderate to an uncomfortable 90F or so over a course of days, at which
point the wall's ability to absorb a given day's heat (thereby making the
house feel cooler) will be all but lost. The house will feel like an oven.
By the same token, in a cold climate where the mass wall's core temperature
dips to 25F, the heat plant (whether passive solar, woodburning, whatever)
will be working to not only heat the interior, but the infinite-heat-sink
of mass wall which keeps dumping the warmth outside.

	Just like the wetting and drying regimes I mentioned in the last post,
these are warming and cooling regimes. If a wetting regime isn't matched by
an equal or greater drying regime, walls stay damp. If a warming regime
isn't matched by an equal or greater cooling regime, walls stay toasty.

	Strawbale might be the better answer for those climates where the extended
average seasonal temperatures are fairly well above or fairly well below
the comfort level, since it has about two inches of highly-insulated dense
mass on all the interior walls... just enough to accommodate diurnal swings
effectively without it turning into a losing battle, and in such an
arrangement (extremely well insulated) that the real financial costs (if
any) of heating or cooling the mass are minimal.

	I don't know if it means anything that FC was patented in 1928; if it
does, let me interject that the first (of several) strawbale patents was
issued about 40 years prior to that, in 1880.

	Also on that subject, it should be pointed out that every one of Mike
McCain's objections to strawbale construction given on page 14 of Earth
Quarterly #1 is answered by one or more lower-cost and easier options...
and several of his broad assertions were exactly wrong. I know that they
there were his comments, not yours, and that you don't necessarily agree
with them. I feel compelled to point out, however, that the only validity
his comments have is in the context of a couple of needlessly-restrictive
strawbale codes which exist in contrast with proven viable strawbale
techniques (such as using them in a loadbearing capacity) and other codes
adopted in other municipalities. I find it alarming when somebody
authoritatively compares an apple with an orange, when all they've ever
done is licked the outside of the orange. Of course it was bitter; he
didn't take the time to get to the good stuff. But I guess it's better to
have a bitter outside and a sweet core than vice-versa. If you'd like me to
answer his extended quote point-by-point, I will, but not to the cob list,
where it would be too far off-topic. I'll happily answer it to the
strawbale list, or privately. And you can be assured that I won't be
speaking in any sort of authoritative manner about FC until I actually have
some sort of authority in the subject... which is what I'm pursuing with
you here, with all my questions and skepticism. I really do want this stuff
to be the cure-all that it might be.

	I'm still not sure what to make of the moisture question. On one hand,
there's somebody soaking down his floors for 2-1/2 years to grow snails...
on the other hand, "[f]ibrous cement absorbs water, so precautions must be
taken to prevent this, especially in wet climates." It soaks up water "like
a sponge" and doesn't deform under saturation conditions, yet you can press
on it when it's soaked and water seeps out (which indicates deformation
from simple hand pressure). Perhaps I'm looking for answers where none
exist. I do that fairly frequently.

	I'll look forward to any information, observations, thoughts and ideas
that you'd care to impart; my ears and mind are open and waiting.

*

For what it's worth, this review will be in the next issue of The Last Straw:

"Mortgage-FREE! Radical Strategies for Home Ownership" by Rob Roy

With just over 350 pages of insightful exposition, practical & manageable
steps, and exemplary representative tales, all offered to aid individuals
and families in the goal of creating mortgage-free lifestyles, this book is
a point-by-point treasure trove of mind-unblocking, wallet-liberating
techniques and methods. I don't consider the strategies to be "radical," as
the subtitle suggests; I consider them to be proven common-sense ideas and
approaches which are too little-known and infrequently-employed in
contemporary Western lifestyles. Perhaps that does make them radical after
all.

It's not a how-to-build-a-house manual, and isn't meant to be; yet the
greater portion of the book covers precisely that, including construction
details. However, the process of living mortgage-free for those of us who
haven't won the lottery doesn't begin anywhere near the process of
building: it begins with taking the steps toward developing and cultivating
the physical, emotional, and intellectual tools to do so. Those are the
most important attributes... and with simple efforts taken toward a true
conserver lifestyle, the financial picture will begin to shape itself up.
One success feeds another.

The book's author favors cordwood construction, but clearly and repeatedly
states that methods using local indigenous materials are always the
"correct" methods... and gives good time and press to straw-bale,
timber-frame, adobe, underground, etc. (Fans of underground housing might
note that Malcolm Wells illustrated this book.)

The only difficulty this book (or any other) can't overcome, which the
author very plainly admits, are needlessly-prohibitive laws and fees that
make the final phase of the effort - that is, building a truly low-cost
home, safely - nearly (or actually) impossible in most, if not all,
American urban areas and many industrialized overseas nations. Despite
that, this book has value for those who wish to live in an urban or
suburban setting. If the goal is not to build, but rather to minimize the
deleterious financial consequences of taking a mortgage, substantial
savings can be realized through simple means and adjustments to create a
less unfavorable payment plan... and more significantly, a saner financial
lifestyle.

Mortgage-FREE! ($24.95 USD) is a Real Goods Solar Living Book published by
Chelsea Green. It can be ordered from any bookstore, Real Goods, Chelsea
Green, or directly from the author: Rob Roy, Earthwood Building School; 366
Murtagh Hill Rd; West Chazy, New York 12992; 518-493-7744
<http://www.interlog.com/~ewood>

*

At 11:13 AM 7/22/98 -0600, you wrote:
>        I'm the editor of Earth Quarterly and the source of all those
>exclamation points about fibrous cement.

	I work for The Last Straw, and may or may not be the editor. It depends on
who you ask. Ask me, and I'll tell you that I'm an associate editor. Ask
the managing editor, publisher, or former publishers and they might tell
you otherwise. I'm thinking that I may just stop fussing about it and
accept the title - I'm extremely proud of what we're doing. (Hey
subscribers - wait'll ya get a load of the new look!)

	My name isn't MJ Epko, it's Mark Piepkorn. (The alias is a long story, and
not a secret; it's how I divide my personal life from my 'professional'
life on the internet.) I tell you this only so that you'll know, not that
it should matter one whit.

>I am presently building a small
>structure (16x16 feet) out of f.c.  I have infinitely more hands-on
>experience with the stuff than I did when I wrote my first article, so you
>can expect the f.c. coverage in the next issue of EQ to be far more nuanced.

	I have absolutely no experience with FC, but if TLS is going to report on
it I'm going to find out everything that I can from you and anybody else
who has the patience to deal with me.

	The rest of your message is requoted for the benefit of the people on the
strawbale list, who didn't get to see it. If anybody wants to see my post
that this one is in response to, see
http://www.deatech.com/natural/coblist/coblist-web/1206.html or email me
sometime in the next couple days if you don't have WWW access and I'll copy
it to you.

>        First, I need to point out that our front cover said, "How to build
>a paper house for 75 cents a square foot."  People have asked me, "Is that a
>typo?"  Others think I'm conning them.  Others flat-out don't believe me.
>However, there are many people, including myself, who are honestly intrigued
>by this amazingly low cost figure.  (It should be pointed out that we are
>talking about materials only, and the cost of the mixer isn't factored in.)
>        I visited Mike McCain and Sean Sands three times, spoke to them at
>great length, watched them at work, helped them a little, and I had, and
>still have, no reason to disbelieve the low per-foot cost they were quoting.
>But face it -- what do you get for 75 cents a square foot?  No foundation,
>no windows (Sean uses glass bottles), an exterior coating (on the house of
>Sean's that appeared on the EQ front cover) that may or may not work.  I
>would love to visit Sean's house the morning after a 3", all night rainfall
>(yes, such rains do happen every few years in southern New Mexico).  If the
>interior of his house is still dry, then this would be a significant fact
>worth reporting.  If the interior is soaking wet, then some redesigning work
>would be called for.
>        Sean Sands' work in particular is very innovative.  He has reported
>a cost for his domes of 39 cents a square foot.  Like everyone on the
>cutting edge, he is going to make mistakes.  But he and Mike McCain are
>pioneering building methods that potentially have revolutionary
>implications.  There are millions of people in the US (and billions
>worldwide) who would appreciate the opportunity to have a snug shelter that
>costs next to nothing.  Not everybody requires a house that is up to
>middle-class standards.  If it's snug, dry, and keeps out the elements, what
>else do you really need?
>        And I really enjoy the science fiction quality of people living in
>structures made from the detritus of a decadent and decaying civilization.
>        A dry fibrous cement block will absorb water literally like a
>sponge.  This is a limitation that can be worked with, however.  Eric
>Patterson of Silver City, NM (he's the granddaddy of the present f.c.
>movement) has done a lot of experimenting, and has found something that
>really works:  He paints on a layer of Home Star silicone coating, lets it
>dry for a couple of days, then covers it with Elastomeric coating.  (This
>will of course increase your per foot cost, as will nuances such as a
>concrete foundation, windows, etc.  My motivation for promoting 75c a square
>foot was to say, "Hey, this is POSSIBLE.  There are people who are REALLY
>DOING THIS.  Such a primitive house might not be your style, but you can
>modify it with more expensive components, and it's STILL gonna be cheap.") 
>        A saturated f.c. block will retain its shape, even under load, but
>you can pick it apart with your fingers if you work at it.  Eric Patterson's
>dome was left uncoated for the first year before he finally coated it.  It
>got completely saturated with water from heavy rains -- you could press on
>the lower course of blocks and water would ooze out.  His dome went through
>repeated saturation/drying cycles.  He says that he didn't notice any
>structural problems.  But nobody would recommend leaving a f.c. strucuture
>open to the elements year after year.
>        I would recommend building a f.c. structure on a concrete
>foundation with a moisture barrier to keep water from wicking up into the
>f.c.  Galvanized roof edge between the f.c. and concrete is advisable --
>Eric has had problems getting caulk to seal the crack between these two
>dissimilar substances.
>        F.c. is a remarkable substance.  Its limitations can be anticipated
>and compensated for.  However, it's not for everybody, and it's not for
>every climate.  It dries VERY slowly, and I think that in a cool, wet
>climate with high humidity, newly-made blocks might take forver to dry, even
>if they were covered from the rain.
>        Then there's the issue of the mixer.  Many people, especially
>"sustainable types," don't particularly like machines.  With f.c., first
>you've got to build your mixer, then you've got to spend many hours having a
>close relationsip with it.  A mixer of my design (which will be described at
>great length in the next issue of EQ, out in Sept.) costs approx. $350 using
>all new components.  If you're going to build only one house, you've got to
>add this $350 onto the cost of your house.  You can buy a lot of straw bales
>for $350.  I think that ultimately, f.c. blocks will be manufactured in huge
>numbers by factories that can take advantage of the economics of scale.
>Perhaps a cost-effective and environmentally benign waterproofing agent can
>be found that can be added directly to the slurry.  At present we have a
>hardy band of f.c. pioneers, inventing their own mixers and mixing their own
>slurry.  This is the equivalent of making your own straw bales by hand
>before you build a straw bale house.  It CAN be done this way, but
>ultimately there will be far more efficient ways of doing it.  (Eric
>Patterson has recommended to one would-be f.c. factory that they make their
>blocks slightly oversized, then mill them to exactly the same size.  That
>way, they could be glued together rather than mortared with f.c. mortar,
>eliminating the need for equipment altogether.)
>        I think Mike McCain has the right idea -- buy a large stock tank
>(used if possible), use a car rear axle/differential (available for next to
>nothing), and power it with a vehicle.  This gives you a very cheap, very
>powerful mixer that lets you do some serious production.  But most people
>I've talked to prefer a smaller, electric-powered design that costs a lot
more.
>        Laura and I have time to mix only one batch a day (if that), so we
>are making slow (but steady) progress on our building.  After the initial
>start-up frustrations and mistakes, we have a pleasant production routine
>worked out.  F.c. is an intriguing material, to be sure.  And we do get a
>special thrill whenever we throw our junk mail into the mixer.
>        I'd be happy to answer any questions anybody might have about f.c.
>
>                                        Happy building,
>
>                                        Gordon Solberg
>
>
>EARTH QUARTERLY
>Box 23-J
>Radium Springs, NM 88054
>
>$10/year
>
>www.zianet.com/earth
>earth at zianet com



   ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   Freewheeling autonomous speculation - Think!
      Personality #7 represents only itself.
    M J Epko - duckchow at mail2.greenbuilder.com
               Kingston, New Mexico
   ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
     That best portion of a good man's life,
     His little, nameless, unremembered acts
     Of kindness and love.
                        - William Wordsworth