Fundraiser Seeks $12K to Update US Building Codes with Fire-Rated Hemp-Lime Walls

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Written By Jean Lotus

A fundraiser to pay for an update to the 2027 International Residential Code has already raised more than $5,000. Photo courtesy of Givebutter

Fundraiser Seeks $12K to Update US Building Codes with Fire-Rated Hemp-Lime Walls

By Jean Lotus

A group of natural building code experts and building pros submitted updates this summer to the US residential model codes that will make it cheaper and simpler to build with hemp-lime (“hempcrete”). An online fundraiser seeks to raise $12,000 to fund the updates to the 2027 International Residential Code (IRC) that will include ASTM tested 1-hour fire-resistance rated walls. Residential building codes are updated in three-year cycles.

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“The original IRC 2024 Hemp-Lime code did not include proof of fire resistance in a one-hour fire test,” explained Berkeley, CA-based architect Martin Hammer, the named lead proponent on the hemp-lime proposals. “Currently, building departments could still ask for an (ASTM) E119 test in cases where 1-hour walls are required, leaving homeowners and builders facing potential significant delays and additional expenses.”

A small group of professionals have already invested their own time and money (about $10,000 so far) to submit 2027 updates to the IRC. The dedicated team of code consultants—Hammer, David Eisenberg, Anthony Dente, Tim Callahan and others—contributed countless hours of expertise built over decades of work with natural building materials. 

“Anthony, Martin and David are very literally the fairy godfathers of the hemp-lime and other natural building appendices,” Cameron McIntosh of PA-based Americhanvre Cast Hemp told HempBuild Mag.

Updated 2027 proposals will be considered at the IRC Committee meeting hearings in Cleveland in October, with the team optimistic about approval.

HempBuild Magazine, Americhanvre, The Hemp Building Institute, Hemp Build School and others have joined together to raise money to fund the new code updates. 

The campaign has already raised more than $5,000, about 40% of the $12,000 total funds needed. A list of thank-you gifts include hemp t-shirts, workshop tickets, books and an overnight stay in a hempcrete stargazing villa.

See the Fundraiser HERE.

Recent History of Hemp-Lime in US Building Codes

The initial push to include hemp-lime in the 2024 International Residential Codes (IRC) was a multi-year project led by Jacob Waddell, founder of the Nashville, TN-based  Hemp Building Institute who was then-president of the US Hemp Building Association. US and international hemp building experts volunteered hundreds of hours to draft the code language. The effort raised more than $50,000 to achieve code approval.

Code warriors Hammer, Eisenberg and Dente acted as consultants to shepherd the document through the code approval process in 2022. The result was Appendix BL, hempcrete’s first appearance in the model US building codes. 

“Since hempcrete was approved in the 2024 IRC, it has opened doors,” Waddell told HempBuild Mag. “We have started to see hempcrete adopted in Austin, TX and now the state of Minnesota,” he said. "When we can codify fire resistance, the more we can add to our competitive argument for hempcrete. This is a huge step forward,” he added.

The International Residential Code Committee votes to approve hemp-lime in Rochester, NY in 2022. Photo courtesy of Martin Hammer

Industry Collaboration and Sharing Data

The updates to the 2027 IRC wouldn’t be possible without hemp building companies sharing data to help the entire industry. 

The new proposed revisions to the 2027 IRC are based on the results of ASTM E119 fire-resistance tests safety test data performed in 2024 and 2025 by PA-based Americhanvre as part of a $1.9M US Army SBIR contract. The revisions new also include a declaration that hemp-lime does not exceed the IRC flame-spread limits for all insulation materials, as demonstrated by 2020 ASTM E84 flame-spread test data performed by Idaho-based Hempitecture, Inc.

The Americhanvre testing of three different wall assemblies was conducted at Intertek, each matching a commonly used hemp-lime wall-framing configuration already outlined in Appendix BL. “This wasn’t about promoting a single company’s product,” McIntosh said, “It was about creating test results that would benefit the entire hemp building industry.”.

An Americhanvre hempcrete wall assembly after passing a fire test. Photo courtesy of Americhanvre

“I tried to keep them as close as possible to what we had written in the IRC document, Appendix BL, to create that resonance between the code work that’s happened and what we were testing,” McIntosh said. “The goal all along was to get to this point where we’re getting it into code, where it has a broad impact for the entire industry.”

Hempitecture’s E84 testing was completed in 2020 as part of the Minka Project outside Austin, TX, co-founder Mattie Mead told HempBuild Mag. The company performed the tests at Intertek which yielded the lowest possible value of zero for both flame-spread and smoke developed indexes.

“One of the biggest gaps in the data supporting hempcrete for this project was its fire resistance. This was a critical component of greenlighting this project,” Mead said. “When we got the results, we knew that it was something that we needed to share and make public, because it is just a critical validation point.”

Fire Resistance is Crucial

Even though hemp-lime has been proven fire-resistant in the EU for decades, US building departments are seeking confirmation that hemp-lime is fire resistant.

Even more so as wildfires threaten residential areas in the United States. “Fire is a rapidly increasing issue for building departments and everyone else,” code co-author Eisenberg told HempBuild Mag. “Having evidence that these are better than conventional construction in terms of fire safety is a big issue.”

Benefitting the Whole Industry

If approved, the code changes will save hemp builders and homeowners time and money. 

For example, in 2023, Karen Rugg of Sisters, OR-based Perennial Building had to provide fire-resistance testing via ASTM E119 tests for a commercial project. Had this testing already been in the code, “I would have saved myself $8K,” she told HempBuild Mag.

Once approved, these updates won’t automatically be available everywhere. The IRC serves as a model code adopted by 49 of the 50 states, but each state and local jurisdiction must specifically adopt the appendices. 

However, even in jurisdictions that haven’t formally adopted the appendix, builders are finding ways to reference it. Code co-author Tim Callahan of Asheville, NC recently worked with a Virginia county that agreed to review a project under the 2024 code through a code modification process, even though the state hadn’t officially adopted it yet.

"It's crucial when you're building with hempcrete to talk to your building officials at the very outset and get them on board," Callahan advised, "because they're the ones who can make or break your project.”

Inclusion of hemp-lime into in the IRC was a big lift, but the code will likely be refined and improved during each three-year cycle, code consultant Anthony Dente of Berkeley, CA-based Verdant Structural Engineers toldHempBuild Mag.  

“[Appendix BL] is a living document that is well-developed but definitely imperfect and it’s going to be on the shoulders of the community to to probably want to regularly be updating things it and advancing it for wider use,” Dente said.

The 2027 IRC updates to Appendix BL are more than technical improvements—they represent the maturation of hemp building from alternative construction method to mainstream building system. With proper fire testing data, refined technical specifications, and a growing track record of successful projects, hemp-lime construction is ready for the next phase of growth.

The whole industry benefits when building codes are updated, said McIntosh, who urged members of the hemp building industry to give to the fundraising campaign.

"The majority of hempcrete homeowners and builders are motivated, capable people who would love the support of the code to put their code enforcement at ease," explains McIntosh. "This is ultimately who this is helping."

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