Straw Bale Construction: The Ultra-Ecological House
Issue: Fall 2018
Author: M.E.A. (“Mea”) McNeil
Topics: Climate Change, Ecology, and Sustainability, Work, Education, and Community, Science, Engineering, and Invention
Locations: California, Arizona, Worldwide, England, Nebraska
Materials: Carbon, Plants, Straw
As our environmental challenges mount — from devastating wildfires to hurricanes and floods — one solution, largely ignored thus far, may lie in using an unlikely-sounding material for home-building: straw. Has the lowly straw bale home’s time finally come?
By MEA MCNEIL
Since the early years of the straw bale renaissance, in the 1970s, when simple, shoe-box designs were the norm, straw bale architects have become more sophisticated. This residence in Sonoma, California, is one example. photo courtesy of John Swearingen/Skillful Means
One warm night in October, 2017, Ed Doody awoke abruptly to see trees, just yards away from his window, burning like paper. The blaze was one of a dozen historic fires that year in Northern California; this one had quickly swept north into Doody’s neighborhood in Mendocino’s Redwood Valley. A fierce wind whipped the flames directly toward Doody’s house, which was constructed with straw bales. Doody and his dog sought refuge in a charred clearing where they were pelted by hail-like embers. By the time this fire was out, it had burned 36,523 acres, destroyed nearly 500 homes, and taken eight lives, four on Doody’s ridge. But Doody’s straw bale house was left standing.
By this October, a new, thousand-fold larger conflagration, the largest in California history, had already burned over the summer just a few miles away, and experts promise more to come.
Meanwhile, in Joshua Tree, a giant, cactus-studded park 650 miles south, in the California desert, lies another straw bale house with a magnificent vaulted ceiling. Built 16 years ago for the late composer Lou Harrison, the home sits near six earthquake faults that have produced two major earthquakes in the past decade. Smaller quakes shake this area about 600 times a year, yet Harrison’s house, and its vaulted ceiling, have held just fine.
What’s going on here? Here’s a building material that’s not only tough, it’s also plentiful, easily renewable, and nontoxic from start to finish. As we will soon see, it can help stop climate change, by gathering a lot of the airborne carbon dioxide that contributes to the greenhouse effect (a process called sequestration). Straw bale walls also hold up well against gale-force winds, like those that recently devastated the Carolinas. As environmental challenges of this nature accumulate, why aren’t we making greater use of this stuff? Shouldn’t straw be housing the world?
STRAW HOMES, REINVENTED
After straw bale workshops, builder David Eisenberg was constantly astounded by the reactions. “People would be brought to tears. I’d walk away thinking, ‘What is this? This is [just] a wall system.’”
The Harrison house is frameless — called “Nebraska style” after the turn-of-the-20th– century houses built on homesteads in the state’s Sandhills prairie. With no trees for structure and sandy earth that would not hold sod, the settlers stacked baled straw out of desperation. The houses proved comfortable in extreme heat and cold, and, by one account, quiet enough for a card game in a tornado. An exodus from the Sandhills during the Depression left behind a building method that was cheap and functional, but seen as déclassé.
If anything, a straw bale home might be one of the most timeless designs. When masters deliberate the meaning of craftsmanship, they often talk about durability — the idea that, in order to have integrity, the items you make must stand the test of time, both functionally and aesthetically. A straw bale home might be a pretty good example of this principle.
No one is sure who started the modern straw bale building revival. Some point to the publication, in 1973, of “Shelter”, a book of yurts, domes, and divine proportions; the book had one page devoted to old baled “hay” structures. Another story is that when a Sandhills church wall was repaired in 1976, a window was added to show visitors its straw-bale makings. Whatever the case, these “truth windows” (called “honesty windows” in the U.K.), became part of a new tradition that spread spontaneously. Within a couple of years, Matts Myhrman and the late Judy Knox, a pair of Arizona straw bale advocates who are called the grandparents of the revival, started teaching the technique.
Baleheads, as straw-bale builders are sometimes called, have long had no codified philosophy, just a set of shared, passionate values. David Eisenberg, a former contractor who got in early on the straw bale revival, traces that to Knox. After a workshop, when Knox would gather the dozen or so participants to meet inside the structure that they’d built that day, “Every time I was astounded,” he said. “People would be brought to tears. I’d walk away thinking, ‘What is this? This is [just] a wall system.’”
Perhaps Knox had tapped into a zeitgeist — an increasingly unmet need. Here was a chance at handwork for anyone who felt like they were losing touch with their surroundings — people who were using electronics they didn’t understand, and driving cars they could no longer fix.
Unfortunately, when these new converts set out to construct their own straw bale homes, they found that local building departments were so unfamiliar with the method that permits in regulated areas were difficult to obtain. “I felt we were seducing people into something they couldn’t do,” Eisenberg says.
Even when permits were issued, the straw was reduced to function solely as insulation — infill for a frame made of wood. On one level, this worked fine. Straw is a hollow tube, the fibrous stalk that remains after the grain head is harvested; when compressed into bales, which are typically 16 to 24 inches thick, straw insulates magnificently by trapping air, much like bird feathers or animal fur. Meanwhile, other benefits of baled straw have gone ignored.
ANSWERS HIDDEN IN PLAIN SIGHT
“From the beginning, it was not an easy sell,” Eisenberg recalls. “I began to question why it was so much harder to get building permits for sustainable buildings than for the most toxic, wasteful building systems.” After studying the problem, he says, “I realized that the codes are exclusively designed around industrialized building. And no one was responsible for the large and serious consequences.”
A 4-by-8 wall panel insulated with polystyrene foam produces 39 kilos of CO2. In contrast, an equivalent straw bale panel actually removes, or sequesters, 78 kilos of CO2 — an improvement of roughly 300 percent.
Just for starters, consider the stunning difference, regarding climate impact, between standard insulation and straw bales. Chris Magwood, a sustainable builder who has written widely on the topic, calculates that a 4×8 wall panel insulated with polystyrene foam produces 39 kilos of CO2, factoring in both manufacture and installation. In contrast, an equivalent straw bale panel actually removes, or sequesters, 78 kilos of CO2 from the atmosphere. Why? Any plant-based material, such as straw or wood, absorbs CO2 through photosynthesis. If left untouched, that CO2 is normally released again later as the plant matter decomposes. However, when straw or wood is used in construction, the fibers don’t decompose. Based on Magwood’s figures, the difference between these two panels is roughly a 300 percent improvement in CO2 with the use of straw.
To John Swearingen, who built the Harrison House, it wouldn’t take much for building regulators to deal with those consequences. “It only takes a small expansion of their scope to consider materials, and then expand that a little bit to the environment. Go up the manufacturing chain or ask what happens to the waste products of the building in the long run, over decades, into the ground, into the groundwater.”
AN IDEAL INSULATOR
The insulation value of straw would seem the least arguable attribute to measure, but it has been difficult put a definitive number to it. Starting in 1994, several tests, including those by Sandia Labs, the Oak Ridge National Labs, and The Canadian Society of Agricultural Engineers came up with different figures for a straw bale’s R-value, which has to do with resistance to thermal conductance.
As it turned out, R-values on straw vary depending on the type of straw being used, and how densely it was packed. A bale wall works by trapping air, the real insulator, in small enough chambers to prevent prevent convection loops. (These are circulation patterns of warm and cool air.) When measured by the inch versus other building materials, a bale is not ideal; its thickness is what makes the difference.
A typical conventional building can take 20 minutes to a couple of hours to adjust to outside temperatures (giving them an R-19 rating). Straw can do much better than that. When plastered over, straw bale walls adjust to temperatures extremely slowly, sometimes over a period of weeks. By the time the outside goes through its diurnal swing, the temperature flow in the bales reverses. So whatever the number — which has been estimated as anywhere between R-32 and R-64, according to the California Energy Commission — straw bale walls excel because of their thermal lag. “The temperature changes are so gradual that physiologically, your body adjusts,” Swearingen says. “It can fall to 63 degrees before you feel uncomfortable.”
The U.S. Department of Energy came to a similar conclusion. In a 1995 report, the agency found that well-built straw bale construction “could provide up to a 60 percent reduction in building heating loads over current practice.” Finally, in 1996, Eisenberg and Myhrman won a significant victory: In Pima, Arizona, they established the first building code that would let contractors use straw bales in load-bearing walls, without the aid of any framing.
Although Eisenberg went on to fight for straw’s wider acceptance, the Pima code, copied in a few other places, was as far as it got for nearly 20 years. “We knew we needed to know a lot more than we did,” Eisenberg says. To get much further, it was clear straw’s advocates would need test data, but funding for testing was scarce. And since building methods in the bale community were open-sourced, the construction industry had no incentive to invest in materials and procedures that could not be patented.
TRIAL BY FIRE
In San Antonio, at 11:10 a.m. on July 19, 2006, the warehouse at Intertek Testing Services registered 90°F, humidity 74°F. Bruce King, an engineer who has written technical books on straw bale building, was there with Myhrman, Eisenberg, and Frank Meyer, a builder who wrote a country song called “Straw and Clay.”
“The most important, unusual, and seemingly counterintuitive feature” of a straw-bale wall, says Bruce King, an engineer, is that it breathes.
To this point, only a couple of small-scale tests for fire had been done on straw bale walls — apart from Swearingen’s propensity to take a blowtorch to a bale to convince doubters of its resistance. So King had arranged for a definitive test. Conducted and certified by Intertek, a Quality Assurance contractor, the test was designed to meet the standards of The American Society for Testing and Materials (ASTM).
The team began by wheeling a 10-by-10-foot, cement-stucco plastered straw bale wall into place in front of the gaping opening of an enormous furnace, then stepped back as six propane burners ignited. A solid vertical sheet of fire soon licked at the wall’s face. It burned at over 1700 ̊F for 2 hours as they watched. The wall stood.
That was just stage one. For the second test, the team wanted to verify what remained of the wall’s structural stability, so they sprayed the burned surface with a firehose “with enough force to knock a man off his feet,” King said. The wall held up just fine. When they removed the plaster from the unexposed side, the bales weren’t even charred. King’s plastered straw bale wall subsequently got an ASTM 2-hour fire rating — twice what comparable wall of wood and synthetic insulation would get.
No one is saying that straw bales alone can save a house. “They’re fire resistive,” says David Arkin of Arkin/Tilt, who designed the house. (In fairness, the Doody house had more than bale walls going for it; it also had a galvanized metal roof, concrete window sills, and a carefully kept firebreak surrounding the house.)
“It takes a system,” said Steve Quarles, a fire expert who did an early straw bale fire test at UC Berkeley and is now at the Insurance Institute for Business & Home Safety Research Center in South Carolina. “Straw bale is a good performer. But vegetation, roof, windows, decks — a weak link is all it takes.”
Indeed, although three straw bale houses built by Arkin and his partner Anni Tilt survived Northern California’s 2017 fires, one did burn — a studio with bale walls on only three sides. (And yes, after the fire those walls stood amidst the wreckage.) A similar sight was the charred straw bale walls that were all that remained of a house in Wales that burned that same winter. The Telegraph erroneously reported: “[The house] was constructed using straw, meaning the fire on January 1 ended up destroying the entire house.”
MYTHS, BIASES, AND DENIAL
Throughout the decades that advocates have been fighting for a bale’s myriad strengths, misinformation has been pervasive. At one point, at a meeting of science writers in Berkeley, California, an architect stressed his environmental sophistication by noting that he had designed a LEED building and drives an electric car. “Straw bale?” he said, “It rots.”
Yes, straw does rot, but only if it gets wet for a long period of time. “But so does wood,” Tilt points out. Actually, straw consists of the same components as wood — cellulose, hemicellulose, and lignins — just in less dense form. (Straw will absorb and hold water more than wood does. For that reason, water pipes are typically not routed through bale walls.) Nonetheless, a long-term study conducted in 2000 by the Canada Housing and Mortgage Corporation concluded that “Straw bale walls do not exhibit any unique propensity for moisture retention.”
While the study’s conclusion seems odd, it has a basis: Straw bale builders have long known that any house they construct needs “a good hat and good boots” — in other words, a roof with a wide protective overhang and a foundation that keeps the bales well above grade. This insight came from observing the continuously occupied straw bale structures in Nebraska that have been whipped with snow for more than a century.
“The most important, unusual, and seemingly counterintuitive feature” of a bale wall, King says, is that it breathes.
Unfortunately, this unique attribute created yet another code problem. Builders are typically required to place moisture barriers across a wall. This effectively suffocates whatever the wall is made of, restricting its ability to release water vapor.
When the earthquake test began, the model of the straw bale house started to sway like rubber. As acceleration increased, the sound of cracking plaster became a reminder of the 2005 Kashmir earthquake that killed 100,000 people — in the place where they proposed building. When the movement stopped, the building stood. “No one would have been killed.”
Sonoma County, California, houses a particularly impressive illustration of why these moisture barriers are unnecessary. In 2003, Ridge Vineyards — the winery that helped elevate California wines in the famous 1976 Paris tasting — constructed the largest straw bale building in the U.S. at its Lytton Springs Winery. The walls here, built with earthen and lime plasters, rise up to 23 feet high. They shoulder a range of loading conditions, in varying degrees of humidity — from rain on the exterior walls to the constant humidity inside the winery’s barrel room. None of these walls were built with moisture barriers; for more than a year, the respiration of the bale walls was closely monitored and tested regularly by two scientists who had been commissioned by the California state government. When the tests were concluded, the researchers found that the relative humidity within the walls was “maintained within safety levels.”
FROM QUAKES TO HURRICANES
David Mar’s seismic work for the Harrison House received the engineering equivalent of an Oscar, and in 2005, its adaptation in China received a World Habitat Award from The United Nations. Yet no straw bale building had been through any earthquakes significant enough to prove a straw bale’s resilience. Then, in 2009, Darcey Donovan, a civil engineer who builds straw bale houses in a quake-prone area of Pakistan, gathered supporters of her nonprofit, Pakistan Straw Bale and Appropriate Building. They constructed a full-scale, load-bearing straw bale house on the “shake table” at the University of Nevada, Reno.
When the test began, the house started to sway like rubber. As the acceleration increased, the sound of cracking plaster became a reminder of the 2005 Kashmir earthquake that killed 100,000 people — in the place where they proposed building. The walls shuddered and a long fissure opened along the foundation. As the shaking was heightened to simulate forces of the Kashmir quake, the breach widened, and the intensity was revved up to nearly half as much more. When the movement stopped, the building stood. “No one would have been killed,” said Donovan.
The resilience of these walls to the force of an earthquake begs another question: How would a straw bale home have fared against the furies of Hurricane Florence in North Carolina?
Hurricanes, of course, deliver a double punch — both wind and rain. Let’s take the wind first, because gales and earthquakes share some destructive habits. “The codes for earthquakes and hurricanes are actually quite similar,” says Michael Wich, Director of Building Code Administration and Chief Building Official for the South Central Planning and Development Commission in Houma, Louisiana. Obviously, nothing would have withstood Florence’s angriest winds, but this means that homes on the hurricane’s edges might have done pretty well.
Rains that turn into floods are a different matter. Given straw’s absorbency, a straw bale home will suffer horribly if storm waters permeate it. But straw bale architects and builders have found ways to protect their walls. As David Eisenberg says, “You should only build with straw bales in a dry place and you can make a dry place anywhere.” Some houses can be put on stilts; others, Eisenberg says, can be built with water-resistant walls down low and straw bale walls above.
THE NEXT CHAPTER
To get straw bale construction officially codified, in 2009 Eisenberg decided to work through international construction codes, which are the basis for local building regulations across the U.S. He recruited Martin Hammer, who, backed by input from 25 architects, engineers, and builders, spent a year writing a proposal for the International Code Council (ICC). At a dramatic hearing in Dallas, straw bale building finally made it into the Appendix of the 2015 International Residential Code; several years later, an update of the code was voted into the Appendix for the 2018 code unanimously. Unfortunately, appendix items in the ICC code are optional. Nonetheless, straw bale building is slowly being adapted state by state. And judging from all reports, it’s facing less and less resistance with each application.
Some obstacles to the widespread adoption of straw bale building are perfectly legitimate. For one thing, it’s not particularly practical in urban communities. As King points out, it “is never going to be efficient enough to scale up” because the walls are too thick for cramped cities; even where space exists, stacking bales without a gang of friends requires too much labor. That’s one reason that, per square foot, building a straw bale house costs about the same as a similar house made of more common materials. But King isn’t giving up. “Straw bale construction is the tip of emerging innovation,” he says. “We’re learning to insulate and build with the by-products of food production, rather than highly problematic petroleum products.”
Meanwhile, a few green builders are developing straw bale wall systems that are prefabricated, to cut down on costs and labor. Some already are being made in the UK, Australia, by a facility in Lithuania for the European market, and in Chile; these buildings can be multiple stories high. But no such production has started in North America.
Whatever solutions people pursue, King offers a guiding maxim for tomorrow’s builders: “Don’t move things very far, don’t rearrange molecules very much, and use what you already have.”
HARRISON GETS THE LAST WORD
In addition to being a composer, Lou Harrison was an ethnomusicologist, conductor, teacher, instrument-maker, poet, calligrapher, critic, polemicist, social activist, environmentalist, dancer, playwright, and creator of a puppet opera. He loved the aesthetics of his straw bale home — thick, rounded walls, deep set windows, and the earthen look of the place, like the vernacular inspirations of his music. He described the building’s acoustics as “heaven.”
Harrison liked the community of straw bale, the custom of gathering for a day of construction, like the Amish barn-raising tradition. There was an idealistic stripe to it that appealed to Harrison, who was a devotee of universal communication through Esperanto. The material made ecological and social sense to him, too: “You have something that can feed you and house you. We could grow all the houses needed in the nation!” he said.
Harrison sketched his house ideas for Swearingen and architect Janet Johnston, starting with a long main room to musical ratios, 3:1. But the professionals paused when Harrison added his vaulted ceiling. After all, they were building in the Eastern Mojave shear zone, a network of faults that move up, down, sideways, and at an angle.
In 2001, 3 years after breaking ground, the house was finally completed. In the end, Harrison’s bale-raising was a celebratory affair, with all manner of artists, dancers, and musicians stacking the straw and plastering the mud.
Harrison wrote his final piece there, and the building has been described as his last and finest instrument. The rust-colored arched house, rising up out of the desert, is now an arts and ecology residency center called Harrison House. In 2017, The New York Times reviewed a performance of Harrison’s 1949 Suite for Cello and Harp when it was performed there. “Emil Miland’s cello sounded ten times its size,” the Times said, “and caused the walls to feel elastic.”
Harrison House is now owned by filmmaker Eva Soltes, who in 2008 showed her documentary on Harrison, “A World of Music,” for the local and county officials in Joshua Tree. “They were all there, the mayor, the building people,” she said. “In the film Lou speaks about the years it took the bureaucrats to issue a permit for his house. And he looks right out at them and says,” she paused for a gleeful laugh, “‘The bastards!’”
M.E.A. (“Mea”) McNeil is a writer, organic farmer, and Master Beekeeper, whose work often focuses on sustainability. Mea recently completed an MFA in narrative nonfiction writing at Mills College, where she won the Teppola Nonfiction Writing Prize. She lives in Marin with her husband and youngest son, in a straw bale house.
Topics: Climate Change, Ecology, and Sustainability, Work, Education, and Community, Science, Engineering, and Invention
Locations: California, Arizona, Worldwide, England, Nebraska
Materials: Carbon, Plants, Straw