of German builders, dating back around 400 years, of filling the walls of wood structures with a mixture of loose straw coated with clay (Chiras, 2000). Modern forms of light-clay building were pioneered in Germany beginning in the twenties, but, as with most other natural building systems, did not take off as a major movement until the 1980s. Most current methods involve the shovelling of the mixture into low temporary forms which are comprised simply of two 2-foot-wide sheets of plywood tacked onto both interior and exterior sides of structural posts. The mixture is tamped, before a next lift of plywood is tacked on, and the process repeated. Plywood from the first level is moved up to the third, then the second to the fourth, and so on. If desired, horizontal or vertical reinforcement can be usedfor example, saplings or small dimension lumber at 16 in. (400 mm) on centre. A number of other forming systems can be used with light-clay, using reed mats and other devices, as builders and researchers are constantly innovating new systems. It is also possible to make bricks, blocks or panels with clay and fibre which can then be used in a pre-dried state (Andresen, 2002). Some producers are hoping to eventually automate production and mass market these natural products. One of the great benefits of light-clay is that it can provide much greater insulating values than other forms of earth construction. In fact, the composition of the clay-straw mixture can be varied in a single building depending on preferences for the wall. North walls, for example, can be designed with a larger straw content for greater insulation values, while south-facing walls can be designed with more clay for greater thermal mass characteristics.