Hemp building materials were officially approved for certification in US building codes at a Louisville, KY conference of the International Code Council last week.
At the meeting, the ICC closed the comment period for hemp+lime (hempcrete) construction for inclusion into the appendix of the upcoming new International Residential Code (IRC). This was the final step to approve the appendix as part of the new code. The new code will become official in 2024 with hempcrete appearing under the listing “Appendix BA.” The IRC is the basis for the residential code in 49 of 50 U.S. states (Wisconsin being the outlier).
Hempcrete, a mixture of hemp stalk hurds or “shiv” and lime binder, creates a long-lasting fibrous insulation wall assembly that is fire-resistant, carbon-sequestering and repels mold and pests. Because hemp sequesters carbon in the walls of a building, hempcrete is an excellent zero-carbon building material that can offset the construction industry’s carbon footprint, supporters said.
The IRC approval applies to hempcrete as a non-structural wall infill system using technology similar to that of the straw bale and the cob wall construction, the committee said. The approval “will make it easier for building departments to review plans for permitting [hempcrete]. This provides prescriptive guidance for a sustainable option for wall infill,” the committee added. The committee rated hempcrete for seismic engineering strength and said further testing for fire resistance was needed, specifically under ASTM E 119 and UL 263. In 2020, fire-resistance testing was completed by Hempitecture, Inc. under ASTM E 84, which showed fire resistance at temperatures up to 575 degrees Fahrenheit.
READ MORE in HempBuildmag (Hempcrete Approved for US Residential Building Codes — HempBuild Magazine)