Cob/Cordwood Masonry Hybrid

[Renewables at aol.com]

> Several months ago, I had been discussing with several list members the
possibility of building a natural sustainable home. The materials used to
construct this home would vary depending on what was available locally. At
that time we had been considering a land purchase in several areas, including
SW WI / NW IL, CO / NM, and even N. NY.

Well, we still haven't narrowed our land purchase down to a specific region
yet, so I thought I would continue to research the various natural building
opportunities available to us. Once we purchase our land, this will give us
the opportunity to practice several small to increasingly larger shed /
workshop type projects to gain some owner-builder proficiency in our building
techniques.

One of the over abundant natural building resources available to us in the NW
IL / SW WI is clay and cordwood potential. In many places here, the soil is
relatively thin, with limestone bedrock only a couple feet below the soil. The
top soil is even thinner, giving way to large amounts or red, green, and
yellow type clays. I give hats off to my grandmother who was able to
successfully cultivate a rich vegetable garden from this soil. If the magic of
composting can work here, then it can work in any organic garden!

I have been a fan of Cob for a long time, but wondered how it would perform in
the really cold winters of N. Illinois and Wisconsin. Sustained temperatures
of thirty degrees below zero on either temperature scale can wick the heat
right out of most any dense thermal mass. Also, the sustained 90+ degree F
temperatures with the high 90+ percentage humidity of late August would
eventually raise the internal home temperatures to the uncomfortable stage.
You would end up having a building with its weak points in March and
September. The cold would be catching up with it in March and the warmth in
late August (at least in N. Illinois). 

I realize that folks who live in natural / sustainable types of homes are
accustomed to slightly wider temperature swings instead of traditional type
homes which use fossil fuel or the nuclear electric grid to control internal
temperatures to +/- 1 degree. My family tolerates well the wider daily
temperature swings. Although we still live in a stick build house for now
(until we build), we have already been practicing the widening of our comfort
zone. Our son gets bad nosebleeds in the winter with the lower humidity. Our
fried dust forced air gas furnace is a problem for him. We have greatly
reduced the problem by setting the daily temperatures to 68 degrees F and the
nightly temperature to 60 degrees F. We are perfectly suited to this now and
Patrick has much fewer nosebleeds. The environment is more closely suited to a
passive solar heated house in the winter as opposed to a yuppie stick built
house environment. A sweater for early evening and a nice warm comforter at
night makes us real comfortable. Our two byproducts are: friends rarely come
to visit in the winter as our house is too frigid for them, and a trip to the
neighbors or a friends house results in our feeling of being roasted alive.

I have also been a fan of cordwood masonry. Because of its dual combination of
thermal mass and insulation, it is uniquely suited for climates like the
Midwest. The fact that a typical cordwood masonry wall has a lower R value
than a straw bale wall for example is not a serious problem due to its higher
mass to insulation ratio.

Popular trees are very abundant out here, in fact they are constantly
encroaching on farmers fields. I won't debate farming practices here, but many
of these trees end up in huge bulldozer slash piles every few years as farmers
fight the battle of encroachment. Just like straw, here is a readily available
building item just waiting to be used.

The problem many folks have with cordwood masonry is that it uses cement as
its thermal mass. This is a high embodied energy product. Although a typical
cordwood masonry wall uses allot less masonry cement than your typical
Midwestern yuppie stick built house, any concrete that you can lesson is good
for the environment!

Based on several discussions on several different lists, I have decided to
contact my buddy Rob Roy or Earthwood Building School and ask him some
questions about a Cob / Cordwood Masonry hybrid. My goal is to find a local
solution to natural home construction that doesn't truck building materials in
from 2,000 miles away.

Finally (if you are still with me), here are the results:

Questions: In Northern Illinois / SW Wisconsin our local saw mills do not have
softwood sawdust available (mostly walnut or oak). Is there any way we can use
straw as a substitute for softwood sawdust? Also, in your travels have you
ever encountered anyone using Cob instead of cement based mortars? Also, we'd
like to come to one of your workshops in 1999, what is your schedule like? How
affordable is land in Northern Upstate, NY?

Answers:

1. Chopped straw might work in the mortar, but not as a shrink agent. It would
serve more as a binder. If I were you, I would try a cement retarder for use
when the weather is hot and sunny, and just leave the sawdust (and retarder)
out when the weather is gray and cool. You really shouldn't need the chopped
straw. Get retarder at masonry supply yard. (I assume this answer is for those
folks still using cement mortar).

2. Chopped straw might make good insulation, if chopped small enough so that
it can be easily poured into the insulation cavity of the wall. (I am
envisioning a chipper/shredder or one of the grinders my grandfather used to
grind corn using the  PTO on the tractor).

3. People in Wales actually did build a cordwood/cob house about one or two
years ago. It even has a living earth roof. From the pictures, I would guess
that it has a diameter of 24 to 32 feet, something like that. The cob /
cordwood house is load bearing!

4. We'd love to see you and Sheila at the NY Cordwood Workweek next July. We
haven't finalized the details, but you will be on the mailing list to get the
1999 brochure as soon as it comes out. Yes, land is very reasonably priced in
northern New York.

5. We also expect to do a three day workshop in Apple River, IL 61001. Must be
near you, the dates will be around June 24, 1999. We will get all of the
details finalized next month. Visit our web site:
http://www.interlog.com/~ewood/

Wow, Apple River is on the IL / WI border and about twenty miles from where we
looked at land! Talk about curb side service!

It look like we have some more homework to do and lots more reading to catch
up on this winter (better than a TV sitcom any day!). Also, we are planning on
attending the Natural Building Worshop in CO at the end of June providing
there isn't a date conflict here. It should be a busy summer next year!

Dave & Sheila Knapp
Winnebago, Illinois
http://hometown.aol.com/renewpwr/