“The Three Little Pigs” was not written through the lens of sustainable building, said Paul Lewis, an architecture professor at Princeton University. For those needing a plot reminder: One house, made of straw, blows down. A house made of sticks meets the same fate. But the brick house remains standing, saving lives and vanquishing the villain.
These days, as the planet heats up because of burning fossil fuels — with the built environment accounting for some 40 percent of global carbon dioxide emissions — the moral of the 19th-century fable should be the exact opposite, Mr. Lewis said. “The straw house sequesters carbon; the wood house is pretty good, but the brick house is a carbon bomb that actually leads to climate disaster.”
Mr. Lewis believes that straw can do much more than provide bedding in a horse stable; it can also provide the stable’s frame, walls and insulation. He and his team have showcased the agricultural byproduct’s potential by building a tiny home — the first of its kind, he said — made almost entirely of straw. The cottage, which looks straight out of a children’s book but has some elegant, modern flourishes, sits on a plot of land outside Hudson, N.Y., about 120 miles north of New York City.
The straw house is more of an architectural feat than a new way of building, although those behind it hope that will change in the future.
“The theory of modern architecture is that when there’s a material, it eventually evolves into a form,” said Guy Nordenson, a professor of structural engineering and architecture at Princeton who worked with Mr. Lewis on the project. The straw house experiment shows what that form could look like. The long-term challenge is to make straw as viable as bricks or concrete blocks, but getting to that point will require more research, Mr. Nordenson said.
Straw, which consists of the leftover stalks of cereal grains such as wheat and rice, is ubiquitous, affordable and a natural insulator. And unlike hay, it has no nutritional value. “It already exists as agricultural waste all over the world,” Mr. Lewis said. Straw is usually left to biodegrade or, more often, is burned, releasing greenhouse gas emissions into the atmosphere that contribute to global warming.
Straw itself sequesters carbon dioxide, meaning it captures and stores the potent greenhouse gas, whereas making bricks and concrete releases it. So building with straw is much less harmful to the environment. “Experts have shown that the amount of carbon sequestered in straw grown worldwide on an annual basis is roughly equivalent to the carbon emissions of the concrete industry,” Mr. Lewis said.
Wood also stores carbon, but chopping down trees is not as sustainable. As Patty Hazle, one of the project’s senior researchers, put it: “We’re trying to come up with alternatives to timber, so that there’s not so much pressure on deforestation.”
The straw house is 28 feet tall and has a sleeping loft, a daybed, five windows and a kitchen. It will be used as a guesthouse by five families, including Mr. Lewis’s, that jointly own the land.
A heat pump, powered by a battery system on the premises and solar panels atop a trailer next door, provides heating and cooling. It is the culmination of three years of research, manual labor, and trial and error. The materials cost a little more than $50,000 (a hefty portion of that — $18,000 — went toward the house’s thatch roofing).
Straw has been used as insulation for years, but usually within a wooden frame, with the straw bales hidden, as part of a hippie-chic style known as the straw-bale house. In Nebraska, prairie settlers used straw bales as load-bearing building blocks and then coated them with mud or plaster. But the straw house near Hudson features compressed straw — where the loose and airy stalks are packed tightly together using heat — as both insulation and building block, without hiding the material behind plaster or wood.
Inside the home, in other words, the straw remains visible, like exposed brick, illustrating how Mr. Lewis’s team built the structure by stacking its components together. On the exterior, the house looks like the perfect domicile for a fairy-tale witch, or three bears. But inside, its clean lines and layers of cut-up straw panels, many of them stacked on an angle, evoke modern minimalism, with custom lighting and large windows with views of the land.
Chris Magwood, a manager of carbon-free buildings for RMI, a sustainability nonprofit, had heard of the project. “It was a cool thing to try,” he said. But he noted that adding a simple wooden frame or using entire sheets of strawboard instead of cutting it into pieces would have made the whole exercise much easier and still would have minimized the use of wood.
Several companies build special frames for straw-bale structures, which makes construction go much faster, he said. One company in Sweden just finished a 12-story apartment building made of wood and compressed straw.
Mr. Lewis’s firm, LTL Architects, is also building a straw-bale home in Ithaca, N.Y., using a wooden frame. A straw-bale home is slightly more expensive, in terms of materials, than a traditional home with plywood sheathing and fiberglass insulation — about $2.50 per square foot more, Mr. Lewis said. The manufacturing and assembly cost is higher, a price tag that will go down with increased demand and supply, he said.
But for this project, his team wanted to showcase the straw inside and out, he said.
The goal was to compress straw bales to create sturdy building blocks that would not require a house frame or a plaster coating. During the summer of 2023, team members experimented with a compressing machine, but failed to achieve a density that they could replicate easily. The next year, they decided to experiment with prefabricated, compressed strawboard, which had been used for interior partitions and ceiling panels since the 1940s, but was not widely considered to be a load-bearing material.
The plan was to cut the boards — which are three times as dense as typical straw bales — into pieces and stack them. Team members, including eight students, first used this technique to build what they called “the doghouse,” a miniature version of the 150-square-foot house they intended to build.
Next came the full-sized tiny house, which was built in components over two months on the Princeton campus. Team members used the strawboard pieces to assemble 16 sections of the house, which were then shipped to the land outside Hudson and put into place with a crane over two days.
The team opted not to dig a basement in order to avoid concrete’s carbon problem. Instead, metal poles were driven into the earth to provide a solid base for the house and lift it a foot and a half above the ground. A permeable membrane that blocks rain from entering the home while allowing trapped moisture to escape was wrapped around the strawboard frame.
The last step was covering the house with thatch, a roofing technique that uses water reeds or wetland grass and was popular in Northern Europe. Team members considered using phragmites, an invasive species from Europe and Asia that is common throughout New York. But they concluded it was too difficult to harvest.
So they worked with a thatch expert from Virginia to supply the product and to teach them how to put it together. Earlier this year, they finished covering the house with about 4,000 pounds of thatch, which was sprayed with a nontoxic fire retardant.
Strawboard, for its part, is fire-resistant and only chars, while its density keeps out vermin. Inside, it’s easy to see how the layers work and how the sections fit together. Mr. Magwood, of RMI, said he appreciated the aesthetic the architects were going for, but that the exposed strawboard should have a protective covering, because it had been cut into smaller pieces, which can make the product shed.
“If anyone rubs that wall, you’re going to get a little shower of straw,” he said. Mr. Lewis said this would not happen because the walls are densely compressed and have been sanded smooth, plus any parts of the strawboard that might loosen up some debris face away from the interior.
Inside the house, a minimal amount of wood was used for the loft ladder, a kitchen counter and a daybed. Mr. Lewis said that less than 10 percent of the house’s structure is wood. The thatch could last up to 40 years. But the home, he said, should survive indefinitely.
Mr. Lewis said that there was no limit to how large a strawboard house, built with this technique, could be. The Princeton team built small because they had a grant of $150,000, most of which went toward paying the student workers.
Nolan Hill, a 30-year-old architecture graduate student who worked on the project, sees the potential of tiny strawboard homes. He compared assembling the components of the house to putting together IKEA furniture (although mastering thatching was more complicated and a bit messier, he said).
“It seems like something that people could do by themselves,” he said. “I could see it popping up in people’s backyards, for maybe a mother-in-law house.”
Hilary Howard is a Times reporter covering how the New York City region is adapting to climate change and other environmental challenges.
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