USA: Hemp officially approved as a building material

Hemp was officially approved and entered into model residential building codes in the United States of America (USA), after a hearing overseen by the International Code Council. A new appendix with the techniques and materials derived from hemp that can be used in residential construction was approved, after the public consultation period ended, and will enter into force in 2024, according to the HempbuildMag.

Hemp construction has been going on in Europe for decades, but in the US these techniques were not properly integrated into building codes because industrial hemp was illegal until 2018, when the Farm Bill was passed. Hempcrete is a mixture of chips of the fibrous part of hemp, or “shiv”, and lime, creating a mortar that gives buildings insulating properties. It is fire resistant, sequesters carbon and repels mold and pests.

However, hemp building materials were officially approved under the US Model Residential Building Code after a public hearing in Louisville, Kentuky overseen by the International Code Council (ICC) last week. The meeting, which closed a public comment period for hemp construction techniques (mortar between hemp and lime), decided to include an appendix in the 2024 International Residential Code (IRC).

The new code will be published in 2023 with hemp mortar (Hempcrete) being cataloged in the “Appendix BA”. IRC is the basis for residential code in 49 of the 50 US states (Wisconsin is out). Applies to single- and two-family homes and townhouses. The IRC approval applies to hempcrete as a non-structural wall infill system using technology similar to straw bale and cob wall construction, the committee said.

Appendix BA will allow the use of hemp lime in low seismic risk regions prescriptively without engineering. High risk regions will require an engineering project. While this presence in the residential code listing gives individual home builders a boost, in order for hempcrete to be approved for commercial buildings, approval is still required in the International Building Code (IBC), which governs all variants not covered by the IRC. The IBC is renewed every three years and will be open for applications in 2025.