Hemp-lime wall material, known as hempcrete, has been added to the 2024 International Residential Code under Appendix BL, giving builders a clearer regulatory path for using it in one- and two-family homes. Made from the woody core of industrial hemp, lime binder, and water, hempcrete is not load-bearing but offers insulation up to 15 times better than conventional concrete and can sequester roughly 228 pounds of CO2 equivalent per cubic yard according to life-cycle analysis. The material also buffers indoor humidity through its open-pore structure and resists mold due to the lime binder. However, supply chain bottlenecks remain, as the U.S. lacks enough processing facilities to separate hemp hurd from fiber. Builders still need local adoption of the code appendix, contractor training, and vapor-open wall detailing for the system to work properly. Hempcrete is not a replacement for concrete foundations or structural frames, but it gives builders a carbon-storing, breathable wall infill option. The next phase depends on domestic processing capacity and broader jurisdictional adoption of the code language.
