The structural system of a regenerative building is more than a framework. It is also the building’s primary thermal mass, its first line of climate control, and often its most significant ecological statement. The choice of building material has profound implications for embodied energy (the energy required to produce and transport the material), indoor air quality, moisture behavior, long-term durability, and the relationship between the building and its site. Pangea buildings use materials with low embodied energy that are available locally or can be sourced from waste streams: recycled automobile tires filled with rammed earth, adobe mud brick, cob (a mixture of clay, sand, and straw), straw bale, hempcrete, and can or bottle walls. These materials are not simply alternatives to conventional construction, they are genuinely superior in many respects for regenerative design, particularly in terms of thermal mass, breathability, and ecological footprint.