Plant-based buildings are being reimagined in Maine

By Elizabeth Walztoni, Bangor Daily News Staff

The walls of a straw house are under construction in a former boat shop at a Rockland industrial park. They aren’t the stacked bales of a hand-plastered homestead; they’re panels of compressed Maine plants industrially sealed in Maine wood.

Croft, a young company that expanded here from a former sardine cannery nearby, hopes to shake up the building industry — plus many other aspects of housing, farming, and life in Maine. 

It’s part of a growing network here and across the country reexamining plant-based building materials. The underlying concepts aren’t new, but much of the movement today is focused on capturing carbon from the atmosphere in response to concerns about human and environmental health tied to modern construction. 

The World Green Building Council, an advocacy group for green building methods, found in 2019 that 39 percent of global carbon emissions came from buildings. Construction and materials made up 11 percent of emissions, according to the council. Concern about figures like these has found its way into federal and state policies.

Andrew Frederick, founder of Croft, sees straw as a way to flip those numbers. 

Straw is pest and fire resistant, nontoxic compared with fiberglass or foam insulation, and an effective insulator. Frederick said customers in Washington County have gone two winters in their straw homes without installing a heating system, telling him their body heat keeps the place warm.

A byproduct of harvesting crops like wheat, barley, rye, oats and rice, straw also grows quickly and is considered the best building material for sequestering carbon. 

It isn’t the only option gaining traction right now, but Frederick sees it as the wisest choice for Maine because it uses waste from an existing industry. 

Wood fiber insulation from byproducts of paper and lumber are also lining the walls of Maine homes using a similar philosophy. TimberHP, a Madison-based company, is the first to make it in the United States and last month expanded distribution across the country.

It also received an expansion loan from the state, which late last year saw a federal designation as a technology hub for finding new ways to use forest products. The focus there, too, is sequestering carbon and reducing energy use once the house is built.

Maine is promoting and funding similar concepts through its 2020 climate plan, which laid out strategies for addressing climate change. A draft for the plan’s update lists reducing natural material waste as a top priority to reduce greenhouse gas emissions.

Those strategies are being reviewed for potential adoption in December, according to Anthony Ronzio, deputy director of communication for the governor’s office of policy, innovation and the future.

The drafts also promote the expansion of “circular economies,” where components are created and reused in one area.

Other ideas still gathering steam on the fringes of natural building include mushroom foam, hemp and wool. The mycelium, a mushroom’s root-like feeding system, feeds on straw, needs a controlled environment and must be baked in a kiln before use as foam.

Hempcrete, made from interior hemp stems and lime, is becoming more widely used, particularly in western states. It’s in at least one Maine building, a greenhouse in Acton at the Diggers Cooperative compost company. A Colorado expert will lead a workshop there this month on using the technique.

Few grow hemp in Maine today. The 2018 farm bill made doing so easier, but supply was higher, demand lower and — because it is the same plant as marijuana — regulations stricter than many expected.

The Maine Department of Agriculture, Conservation and Forestry, which licenses hemp growers, had only four licensees in 2023. A 2022 report said the industry “continues to be depressed.”

Sheep’s wool is also used as insulation in the United States and internationally. Croft uses it for areas the patented straw machine’s shapes can’t accommodate.

For many farmers here, wool is a waste product, which is gaining popularity as a soil amendment. Frederick also believes it can be put to good use in insulation and make money for farmers; he buys byproduct wool from a local mill, too.

Intrepid Mainers have gotten creative with natural housing materials like these for decades. Ten years ago, a Milo woman attempted to build a house from “earth bags,” sacks of mud encased in plaster. An MDI home made of “rammed earth,” a method of compacting soil that dates back to Neolithic times, may be the only one of its kind in New England. 

A cordwood house in Abbot, built with a medieval-era process of stacked wood and plaster, made headlines last year. Others have created straw bale homes, fitting straw in a timber frame and plastering them. 

These techniques haven’t gained wide adoption in Maine because the seasons are wetter and the winters colder than the desert climates where they began. A straw bale house in New England needs careful, thick plastering to avoid mold, for example, and plaster can crack in low temperatures.

The methods are also labor intensive, unpredictable and difficult to scale up. Plus, according to Frederick, many people just want a house to move into. 

With straw moving into commercial production, he has more big ideas. It could be grown on PFAS-contaminated farmland, producing income for farmers and contained safely in the airtight panels. Storage facilities for the straw harvest could also serve as community warming shelters. 

People sometimes react to these suggestions with bewilderment. Because they’re used to working in specific fields, combining construction, science and agriculture can be hard to picture, Frederick said.

But he views straw panels as a way to bring Maine together in solving problems like affordable housing, environmental contamination, heating costs and climate change.

For now, the 10-person shop will produce about 10 building envelopes in 2024 and is booked out into 2025. If the business focused on production alone, without permitting and administration, Frederick said they could make 20. The process is getting faster all the time. 

Croft is also setting up a straw supply chain from Maine farmers and looking for more to purchase from.

Ultimately, Frederick would be happy if all Croft did was prove the viability of straw. He’s confident it will become so much stronger, cheaper and better that no one will need convincing, and he wants to eliminate the roadblocks to adoption of the design. 

A straw panel building envelope is at or below the cost of other comparable construction, and provides what he sees as long-term benefits to health and energy use.

“If all we did was prove it could be done, I can retire a happy man,” he said.