Last week, the hemp building industry scored a victory when the International Code Council (ICC) approved hemp-lime (hempcrete) insulation in the model U.S. residential building code at a public hearing in Louisville, Ky.

The U.S. Hemp Building Association (USHBA) submitted Proposal RB316-22 in January to receive certification for hemp-lime insulation in U.S. building codes. The ICC officially closed the public comment period last week.

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“The new code will be published in 2023 with Hemp-Lime (Hempcrete) appearing as ‘Appendix BA’ in the upcoming 2024 International Residential Code (IRC),” which is the foundation for residential code in 49 out of 50 states (aside from Wisconsin) and applies to one- and two-family townhouses and dwellings, according to a press release from the USHBA.

The approval allows hempcrete, “a mixture of hemp hurds or ‘shiv’ (made from hemp stalks) and a lime binder, [that] creates a long-lasting fibrous insulation for wall assemblies,” to be used as a standard material in residential construction in low seismic risk areas without required engineer design beginning 2024. High seismic areas will require engineered design, according to the release.

Editor’s Note: A seismic zone “is used to describe an area where earthquakes tend to focus; for example, the New Madrid Seismic Zone in the Central United States,” according to the United States Geological Survey.

Hempcrete is a natural insulation material with carbon-sequestering properties and is fire-, mold- and pest-resistant. Supporters said that because hemp can sequester carbon in building walls, “hempcrete is an excellent building material that can offset the construction industry’s carbon footprint,” according to the release.

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Martin Hammer, an architect and proponent of Proposal RB316-22, expressed that IRC appendices are voluntary “unless specifically adopted by a state or local jurisdiction,” according to the release. Therefore, before the code is officially adopted in 2024, “designers and home builders working on a hempcrete project may still be required to be approved as an ‘alternative material and method’ by local building departments,” according to the release.

“On the other hand, even now, this well-developed ICC building code appendix ‘Proposal RB316-22’ can be proposed to a local building official for use on a project basis,” Hammer said.

Ana Konopitskaya, a proponent of the proposal and co-owner of Pennsylvania-based Coexist Build, an architecture company dedicated to revolutionizing conventional construction practices, said the certification is “a groundbreaking achievement.”

And Matt Marino, a proponent of the proposal and president and founder of North Dakota-based Homeland Hempcrete, a company that designs and builds homes using hemp materials, said the inclusion of hempcrete in the U.S. building codes helped “add legitimacy” to his craft.

“It is a tool for us to standardize our deliverable,” Marino said. “This is just the beginning, and I look forward to seeing where we can take this industry.”

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Henry Gage Jr., USHBA president and certifications director, also praised former USHBA Executive Director Jacob Waddell for his work and efforts in the certification process.

“I would like to acknowledge [Waddell] for his leadership. With this approval, hemp-lime construction has moved to the mainstream, creating a new era of investment opportunities, research, workforce development, architecture and construction,” Gage said.


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