Today, let us grasp at straw. The University of
Houston's College of Engineering presents this
series about the machines that make our
civilization run, and the people whose ingenuity
created them.
"If you don't let me in,"
snarled the Big Bad Wolf, "I shall huff and puff
and blow your house in." We imagine that was no
idle threat, for the First Little Pig's house was
made of straw. (Do parents still tell children
about the Three Little Pigs?)
Straw is a universal symbol of triviality. Yet when
modern city dwellers speak of straw, they aren't
sure what it really is. It's what's left of wheat
or barley after the edible seeds are gone. Hay is
animal fodder -- dried alfalfa or grass. Hay still
has seeds for food value. Straw is empty and
useless. Or is it!
Two friends recently went to Minnesota. "Vacation?"
I asked. "Well, sort of. It's a workshop on
building houses of straw." I thought they were
joking -- but they weren't.
The trick is to pour a concrete foundation and
embed vertical reinforcing bars in it. Then you
impale bales of straw on the steel. You build a
whole house out of straw Lego blocks.
You layer stucco on the outside and plaster on the
inside. It reminds you of adobe, but adobe is a
true composite material -- an earthen matrix
strengthened with plant fiber. This straw house is
a laminated composite -- a kind of straw-bale
sandwich.
The bales are from three to four feet long. Their
width can vary from just over a foot to almost two
feet. You get a very thick wall regardless of how
you put it together.
Those thick straw walls make remarkable thermal
insulators. The rating is something like R46. You
might as well live in a cave, but for doors and
windows. The construction I've described will carry
a light roof, but no more. If you want a two-story
house, you build wooden truss-work around the
bales.
Straw walls are cheap, but walls are only a
fraction of the cost of a house. You save more
because you can build so much of it yourself.
Straw-bale houses also offer variety. A passive
solar house of baled straw in California's Owens
Valley shows up in a solar energy magazine. A
two-story, 2100-square-foot house in Iowa has 5
bedrooms and 3 baths as well as energy efficiency.
Like any new technology, this one leaves us asking
what the hidden flaw will be. When we first hear of
straw houses, we ask about fire, and we mention the
Big Bad Wolf. But water, not fire, is the straw
house's enemy. The walls must be kept dry.
While we voice our doubts, houses go up. Their
owners are enthusiastic. Some straw-bale houses
have lasted almost a century. Straw is an ancient
byproduct. We've made everything from bricks to
paper from it. Yet we remember the First Little
Pig. And I'll bet that nursery story does as much
to keep us from making straw houses as any frailty
of straw itself.
I'm John Lienhard, at the University of Houston,
where we're interested in the way inventive minds
work.
(Theme music)
Myhrman, M., and Knox, J., First Aid Kit for
Plastered Straw-Bale Construction. 1037 E.
Linden St., Tuscon, AZ 87519: Out on Bale, (un)Ltd.
1993(?).
The Last Straw. Vol. 1, No. 3, Spring
1993.
Haggard, K., and McMillan, G., "Straw Bale Passive
Solar Construction. Solar Today,
May/June 1993, pp. 17-20.
Strang, G., Straw-Bale Studio, A Cheap, Sturdy
Structure with Good Thermal Performanace.
Fine Homebuilding, No. 24, December
1984/January 1985, pp. 70-72.
Glick, T.F., Cob Walls revisited: The Diffusion of
Tabby Construction in the Western Mediterranean
World. Humana Civilitas: Sources and Studies
Relating to the Middle Ages and the
Renaissance. Vol. I, On Pre-Modern
Technology and Science. (B.S. Hall, D.C.
West, eds.) Malibu: Undena Publications, 1976.
I am grateful to Karen and Donald Hall for relating
their experience in the straw bale workshop and for
providing the first two sources above. I am
grateful to Jean Krchnak, UH Architecture
Department, and Margaret Culbertson and Pat
Bozeman, UH Library, for providing the additional
materials.
The Engines of Our Ingenuity is
Copyright © 1988-1997 by John H.
Lienhard.
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