Every material we build with has a history before it arrives at the construction site, and a future after the building it was used in has been demolished. The embodied energy of a material — the total energy consumed to extract, process, manufacture, and transport it — is part of the true environmental cost of a building. For conventional materials like Portland cement, structural steel, and aluminum, embodied energy is enormous. For natural earth-based materials, it is close to zero.

The choice of building material is therefore not merely a technical or aesthetic decision. It is an ecological one. Natural building materials — earth, straw, clay, stone, hemp, timber — embody the sun’s energy captured over years or centuries by biological processes. They are typically non-toxic, breathable, and at the end of their life either biodegradable or indefinitely recyclable. They are also, in most cases, available locally, which eliminates the transportation burden that makes many “green” manufactured products less green than they appear.

This chapter introduces the primary natural building materials used in Pangea projects. Each is covered in full technical detail in Book 3 of this series, Earthship and Natural Building Construction.