Straw bale construction: an update
by Alice Martinez
New projects bring this 200-year-old eco-friendly technology closer
to the mainstream
[Ed. note: The Earth Times first reported on straw bale home
construction in our Oct '94 issue.
Since that time, much progress has been made in overcoming the government
regulatory hurdles that have prevented the introduction of this renewable,
sustainable, environmentally responsible technology. What follows is a brief
primer on straw bale building, followed by two articles that describe new
efforts to bring straw bale construction to our bioregion.]
traw bale construction is a responsible gesture toward
Mother Nature, and one that makes sense. Instead of seeing the dry grain
stems burned or buried or simply wasted, this byproduct can be put to good
use. Since cereal grains are grown in most states, there would be plenty
of straw to go around. Straw is an annual renewable resource, unlike timber
that can take 30 or more years to come back.
"Straw is a naturally occurring material, and if
used properly in a structure, it's very durable and also an excellent insulator,"
according to ecological designer Jim Bell. "If a house is built and
serves its purpose for 100 years, the major materials, meaning straw, could
break down and go back into nature. That's what we need to look toward.
In long terms, it's a cradle-to-cradle resource movement."
Straw-bale construction dates back to the last century.
Homesteaders in Nebraska started using straw bale to build homes in the
late 1800s, out of necessity. With timber in short supply, people turned
to the renewable resource they had on hand - straw from wheat, barley and
With the Nebraska method, compressed bales of straw
serve as the main support for the roof. Using this load-bearing technique,
a continuous beam is placed around the house's upper wall on top of stacked
straw bales, and then a roof is put on top of that. (Think of them as big
bricks.) Typically, the bales are pinned together with rebar (steel bars).
The completed structure is wrapped with chicken wire and stucco is applied,
giving the home a conventional external appearance.
Straw bale homes, which have an adobe look to them,
are very attractive because the walls are thick and solid, typically 22
inches thick. They're so thermally efficient that utility bills plummet.
In one test conducted for the federal government that compared utility bills
from conventional wooden homes with bills from straw-bale homes, the straw-bale
houses saved as much as 75 percent on utilities.
They're cheaper to build, too. Straw bales cost about
$10 a square foot to build, compared to $80 to $100 for conventional homes
in San Diego County.
Safe and sane
As far as insects are concerned, straw is usually not
on the menu. Straw has virtually no nutrients and common house eaters, like
termites, devour wood and not straw.
Once covered with stucco or similar material, straw
bale is extremely fire resistant. During a two-hour fire test a section
of a wall constructed with straw bale was placed against a furnace. Within
five minutes, the temperature shot up to 1,000 degrees Fahrenheit, then
1,750 degrees after 60 minutes. Wood catches fire at 500 degrees. If the
wall had been wood, it would have burned. If it had been steel, it would
have buckled. As the temperature on the hot side topped out at 1,940 degrees,
the cool side temperature rose only 12.7 degrees. Code regulations allow
the temperature to increase by as much as 250 degrees and still pass the
In a wind test, the equivalent of a 75 mph gale caused
no movement in a straw bale structure. At 100 mph, it moved only 1/16 inch.
To prove straw bale's superb insulation benefits, testers
examined the material's "R" factor, a numbered rating system used
to determine how well a material insulates. Higher numbers indicate relatively
better insulation. A six-inch wooden wall with fiberglass insulation, for
example, carries an R factor of 19. The average roof rates R30. One bale
of straw without any plastering rated R48.
Straw bale evangelism takes off
by Alice Martinez
Special straw bale workshop scheduled for May 24 -26
ob Bolles was not prepared for the response his straw
bale exhibit received at last month's EarthFair in Balboa Park. "The
response was astonishing," he exclaimed. "We always expect a lot
of 'Three Little Pigs - Big Bad Wolf' jokes, and an equivalent number of
the genuinely curious. I was simply not prepared for the number of folks
who came up to us and said that they had seen a show or article on PBS,
Sunset Magazine, Good Morning America, The Wall Street Journal, and the
local newspaper. This was obviously a much better informed group than I
"We ran out of literature by noon. Flyers, books
pamphlets - even stuff I hadn't planned on giving away - just disappeared."
At times, so many people stopped to watch the straw bale house demonstration
that the thoroughfare in front of the display was impassable.
Bob is a local building consultant, California Straw
Bale Association member and active proponent of straw bale construction.
Bob and his Mexican counterpart Roberto Valdez, from El Valle de las Palmas
(The Valley of the Palms), Baja California, were part of a charter group
of straw bale proponents that met in California Valley (San Louis Obisbo
County) in February to hammer out the objectives of an organization dedicated
to the development of straw bale construction.
"This isn't just about extolling the (many) virtues
of building with this very unique and versatile material; it's mostly about
education," Bob explained. "First we have to continue to educate
ourselves. Next, we must extend that education to our fellow professionals:
architects, engineers, designers - all of the building trades - and the
various building departments. Finally, we need to spread the word to the
general public, just as we did on Earth Day." As part of this education
process, Bob and Roberto have scheduled a Straw Bale Workshop for the weekend
of May 24 through 26. Interested participants need to reserve a space early
due to the tremendous interest.
Demo in Mexico
Roberto is in the process of forming a non-profit corporation
in his home town of Valley of the Palms, 20 miles south of Tecate, Mexico.
There he will build a Sustainable Community Center consisting of a variety
of housing units and a main building in which to conduct classes in sustainable
design and construction. "We have already received inquiries from quite
a number of groups and individuals who wish to participate in the building
and design of the center, and we are beginning to schedule specific dates
for the people to come down and work on the project" he said. "What
is particularly encouraging is the number of youth groups who wish to participate,
although we expect participation by a wide variety of people who are interested
in learning to build sustainably."
One of the most intriguing features of the project is
that the construction of the buildings provides a hands-on opportunity to
learn about straw bale and other sustainable construction practices. As
the buildings are completed, they become sleeping and living accommodations
for the participants who will have the opportunity to experience living
in a straw bale house.
Bob went on to say, "I am focusing on simple house
designs that can be built on either side of the border that are easy to
build, low in cost, and yet conform to the Universal Building Code (UBC),
and the Safety Guidelines for Straw Bale Houses that were established by
AB 1314 which was passed by the State Legislature last year. We are encouraged
by the interest in participation by members of the building professions
- architects, engineers, and the builders themselves. We are looking forward
to their input into the design and construction process.
"At the Earth Day Fair, we talked to a number of
people who want to start building their new straw bale home in San Diego
County just as soon as possible. You may find 'Construction Grade' Straw
Bales at your local lumber yard sooner than you think."
Bob Bolles can be reached at (619) 486-6949 for more information or to
register for the workshop.
Habitat for Humanity goes for straw
by Skip Fralick
Earth-friendly, affordable housing, and you can help make it a reality.
aurie Roberts stirred up some excitement when she built
the first straw bale house in San Diego County in 1994. Her spark may grow
into a flame (sorry, bad metaphor) - her action may inspire the building
of many more SB homes in this area. She certainly inspired me, as the environmental
director of Habitat for Humanity (HFH), San Diego/Tijuana, to choose straw
bale as the appropriate technology for a daycare center planned for Rosarito.
The first straw
The project began in January 1995, when Rev. Laurel
Grey of Lutheran Third World Opportunities offered to sponsor a straw bale
house for about $5,000 if HFH would get the land, design the building, and
supervise 12 high school volunteers coming from Alaska for a week.
I assembled a team whose most experienced member, Jim
Danielson, had attended one workshop. Lynn Nelson burned the midnight oil
to produce a simple plan for a Nebraska-style load-bearing structure, identical
(in terms of interior dimensions) to HFH's 2-bedroom, 480 square-foot homes
typically built in Tijuana. Miguel Hernandez, an architect from Rosarito
and his wife Virginia organized efforts and approvals in Rosarito, obtained
the land, and even fed and housed the Alaskan crew. Straw bales were trucked
from San Ysidro to the site. About 140 bales at $4.50 each were used.
During construction, local farmers were excited because
they saw that, instead of burning their waste straw, they could sell bales
for future homes at say, $1 a bale!
The structure was simple: a 20' by 24' rectangular structure
with bales pinned together with rebar and coated with stucco. Two-by-four
trusses were used as support for the asphalt tile roof.
Rain became a major obstacle, with record rainfalls
the week before and during construction. It was not possible to pour the
footing/stemwall until Tuesday of the construction week, and the Alaskans
were scheduled to leave on Friday! It looked grim, but miraculously a weather
break occurred. The footings were quickly poured, and on Thursday the kids
were building the straw bale walls. They left Friday, with straw in their
clothes and happy feelings.
But the unusually heavy rains continued into May, slowing down weekend construction.
At one point, a man whose sole purpose in life at the time was to cover
the straw with tarps at any threat of rain missed his calling, and the bales
got soaked. After three months, the bales were again dry, except for a dozen
spots which were easily located with a $4 soil moisture probe. These spots
were surgically removed and repaired.
Another dramatic episode occurred when vandals ripped
out a dozen bales and tried to set fire to the house. Neighbor workers were
able to extinguish the flames before penetrating very far into the baled
straw. The tight bales didn't allow much air circulation to support a fire
(Canada has given straw bale walls a 2-hour fire wall rating). The gaping
hole in the wall was replaced with a used 2-glazed sliding door, donated
by Dan Cannon of the Building Materials Recycling Center on Otay Mesa. Bob
Bolles helped repair the damage and prepare the house for stucco.
Recently, a group of neighbor families has joined in. They're planting landscaping,
installing windows and wiring and applying the stucco. A compact fluorescent
photovoltaic lighting package is to be donated by United Solar Systems Corp.
of San Diego.
The daycare center will serve as a model straw bale
home, community meeting center, and organizing point for a grass roots Habitat
for Humanity affiliate to be formed later.
The next step ... it's your turn
Tecate is the site of 40 Habitat for Humanity homes
served by a unique natural sewage treatment system, called a constructed
wetland, with reclaimed water from the wetland irrigating a fruit orchard
and community park. The same Lutheran organization that sponsored the Rosarito
project wishes to sponsor another straw bale building, preferably in Tecate.
This time, the families could co-fund the community center, and would help
design and build it. Planning and permitting efforts are underway with construction
scheduled to start this June.
Beginning on June 23, 75 Lutheran students are scheduled
to camp out and participate. This project will also serve as a demonstration
site, and will serve as a Habitat for Humanity organizing center. The Tecate
families are a well established community. They have a Homeowners' Association
and seem ready to organize another Habitat affiliate to help other low income
Mexican families get decent housing by helping themselves. This is what
Habitat for Humanity is all about!
You can help provide this much needed housing and get
some hands-on experience with this new 200-year-old building technology.
Interested volunteers and donors are invited to call Skip Fralick at (619)