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Substance added to a soil to improve its characteristics.


An earthen building technology: blocks or bricks are formed by pouring a specified mix of soil, water, and straw into molds and drying them in the sun.

Naturally plastic fine soil particles composed of hydrous aluminum silicates and other colloidal substances.

  • Cob

    An earthen building technology: moist clayey soil and straw are mixed to form lumps (cobs) and applied directly onto the wall without mortar or framework.

  • Compressed earth blocks (CEBs)

An earthen building technology: blocks are formed by mechanically compressing a specified mix of moist clayey soil into blocks.


For building purposes, the subsoil layer occurring directly under the top layer of humus or topsoil. Typically a mixture of gravel, sand, silt, and clay.


A structure made largely from a proper mix of soil.


Total energy required during the life cycle of a building material or building — raw materials extraction, transport, processing, manufacturing, delivery, construction, maintenance and repair, and disposal or recycling/reuse. Embodied energy does not include operational energy. 

The ability of materials to absorb or adsorb and retain moisture from the surrounding air.

The ability of materials to absorb and release water vapor and heat from and to the surrounding air. The presence of clay in earthen walls is responsible for the daily modulation of water vapor and heat, contributing to indoor air quality and comfort.


An earthen building technology: loose straw is tossed with clay slip and then lightly packed into formwork. It is used as infill in a post and beam structure and is usually coated with lime or earthen plaster. Because the clay and straw mix is primarily straw and not tamped into forms nearly as forcibly as rammed earth, light clay straw walls are a fraction of the density of rammed earth walls and not load bearing.

Construction where walls are built of a single material, such as rammed earth and cob.

  • Mortar

A workable paste used to bind masonry units that is compatible with the specific type of masonry unit used.  This paste mixture is typically some combination of soil/sand, water, and a binder such as lime or portland cement.

The energy consumed when a building is used. 

  • Passive solar design

Design of a structure to utilize the sun’s energy to regulate a building’s temperature while minimizing reliance on other energy sources.


A soft mixture of clayey soil, water, sand, and lime that is spread on walls and ceilings to give a smooth or textured, hard surface finish. In modern times, lime plaster has been replaced by gypsum plaster, although lime can still be used. In addition, fibers sometimes are added for additional strength. Cement is sometimes added or exchanged for lime for more durability but reduces the breathability of the walls. Traditionally, the term plaster refers to the material used on interior surfaces while stucco is the term used for exterior surfaces, but people often interchange the terms for either interior or exterior.


An earthen building technology: a specified mix of moist soil placed in wide formwork and mechanically compressed, resulting in a monolithic wall which may be load bearing. Stabilization material is commonly added to the mix when exposure of the soil layers is desired.


Clayey soil mixed with water. Slurry is a thick mixture, and slip is a thinned mixture.


Earthen construction (blocks or monolithic) that uses a binder such as lime or cement to increase compressive strength and durability.


Traditionally, a mixture of lime, sand, and water for application, it dries to a hard, durable, smooth or textured finish. 

  • Thermal flywheel effect

The cyclical pattern of  a building element, such as an earthen wall, collecting heat during one period and releasing it during another (such as collecting heat during the day and releasing it at night).

  • Thermal mass

The capacity of a material to absorb, store, and release heat energy due to its density and rate of thermal conductivity.


The degree to which a building material allows the passage of water vapor.


An earthen building technology: a mix of earth and straw is applied into an interwoven lattice of wooden strips and smoothed over.

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