Natural Building Codes In the USA – Update and Overview

Until 2015 there were no provisions for natural building in the U.S. national model building codes, other than an outdated legacy code for adobe, and otherwise a handful of regional codes. That changed with the inclusion of Appendix S – Strawbale Construction, and Appendix R – Light Straw-Clay in the 2015 International Residential Code (IRC). The IRC is the basis for the residential code in 49 of the 50 U.S. states. That was followed by appendices on Cob (Monolithic Adobe), Hemp-Lime Construction (Hempcrete), and a related appendix for Tiny Houses, as well as updates for Adobe in the International Building Code (IBC).

Martin Hammer, David Eisenberg, and Anthony Dente have been at the forefront of this effort to gain wider acceptance and ensure proper use of natural building materials and systems in the U.S. They will take you through this journey, give an overview of the current codes and how to use them, and discuss what’s in process now and what could be next. Never has the need been greater for broad access to natural building codes, as healthy alternatives to decades of building practices that have contributed to environmental degradation and accelerating climate change. Their work with a wide array of colleagues has sought to meet this need.

The event is finished.


Oct 22 2023


2:00 pm - 3:00 pm


Breakout Sessions


Shining Mountain Waldorf: Music Room


David Eisenberg, Anthony Dente, and Martin Hammer


  • Anthony Dente
    Anthony Dente
    Verdant Structural Engineers, Cob Research Institute

    Anthony Dente, PE, LEED AP, is a licensed engineer and principal at Verdant Structural Engineers (VSE) and Verdant Building Products (VBP) and is the vice president of the Cob Research Institute (CRI), where he is committed to appropriate material use for all structural building systems. VSE has designed over 300 structures using natural-building wall systems such as straw bale, adobe, hempcrete, ceb, cob and rammed earth. With CRI, he was the lead engineer for the Cob Construction Appendix in the International Residential Code, as well as the Hemp-Lime (Hempcrete) Appendix, both the first of their kind in the US. With VBP, he is project lead for their prefabricated, carbon-storing, straw wall panels which was originally developed under the EPA SBIR grant program.

    Anthony recently completed authoring Essential Cob Construction, A Guide to Design, Engineering, and Building with New Society Publishers, currently available for presale and set for release in January 2024. He also contributed to the Straw Bale Building Detail book published by the California Straw Building Association (CASBA). He is also on the advisory board of the Last Straw Journal.

    Anthony is a member of the TMS Modular Unfired Clay Standards Committee developing the much-needed contemporary adobe and CEB building code. Dente has advised, designed, and collaborated on numerous university research programs testing the structural behavior of natural materials, and writes and lectures extensively about appropriate use of environmentally sensitive building materials.

    Dente was recognized by the Constellation Prize for his Sustainable Engineering Practice, and he continues as a visionary and leader in the natural and low carbon building fields.

  • David Eisenberg
    David Eisenberg
    Director, Development Center for Appropriate Technologies

    David Eisenberg co-founded and has led the Tucson-based nonprofit Development Center for Appropriate Technology (DCAT) since 1992. DCAT launched their program Building Sustainability into the Codes in 1995 seeking to create a sustainable context for building codes. David’s wide-ranging building experience—from troubleshooting construction of the high-tech cover of Biosphere2, to conventional concrete, steel, masonry, wood, adobe, rammed earth, and straw bale construction—has grounded DCAT’s codes and standards work in real-world building experience. Working with EPA, DCAT led the development of EPA’s Tribal Green Building and Building Code website and a related Toolkit. David served two terms on the U.S. Green Building Council (USGBC) Board of Directors where he founded and chaired USGBC’s Code Committee for eight years. He led the task group that developed the ASTM 2392 Standard Guide for Design of Earthen Wall Building Systems. David served on the initial drafting committee for the International Code Council’s (ICC) International Green Construction Code. David co-authored The Straw Bale House book, helped write the first load-bearing straw bale building code, and helped develop the International Residential Code (IRC) Appendix S: Strawbale Construction (as well as its official Code Commentary) for the 2015, 2018, and 2021 versions. He was also involved in the development and approval process for the IRC appendices for Tiny Houses, Light Straw-clay, Cob Construction, Hemp-Lime Construction and writing their official code commentaries. DCAT and David received ICC’s 2007 Affiliate of the Year Award and a 2007 USGBC National Leadership Award. David serves on the boards of Sustainable Tucson and the Tucson 2030 District.

  • Martin Hammer
    Martin Hammer
    Architect, Co-Director - Builders Without Borders

    Martin Hammer is an architect in California and co-director of Builders Without Borders.

    Throughout his 35-year career he has emphasized sustainable building design, including passive and active solar design, with particular focus on the design, testing, and construction of straw bale buildings. He has written and lectured widely on the subject, including as a contributing author of the book Design of Straw Bale Buildings and CASBA’s Straw Bale Building Details.

    Since 2001 Martin has worked to include sustainable building materials and systems in building codes. He is lead or co-author of five appendices in the International Residential Code (IRC): Appendix AS – Strawbale Construction, Appendix AR – Light Straw-Clay Construction, Appendix AU Cob Construction (Monolithic Adobe), Appendix AQ – Tiny Houses, and Appendix BA Hemp-Lime (Hempcrete) Construction. He has also worked to revise the adobe provisions in the International Building Code (IBC).

    In 2006-2007 Martin helped introduce straw bale construction to earthquake-affected Pakistan with Pakistan Straw Bale and Appropriate Building (PAKSBAB). He was extensively involved in post-earthquake Haiti (2010-2013), including reconnaissance with the Earthquake Engineering Research Institute, historic preservation with the World Monuments Fund, and sustainable rebuilding with Builders Without Borders (BWB), including Haiti’s first straw bale building. From 2015-2019 Martin led a BWB team in rebuilding sustainably in post-earthquake Nepal. He is co-author of A Strawbale Building Tutorial: For High Seismic Regions of the Developing World.

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