The straw bale

Straw bales are stalks pressed into cuboids from threshed and then field-dried cereal plants, not to be confused with dried grass, which we call hay. Hay is much more prone to decomposition in the presence of moisture, probably also because it contains much less air and therefore has poorer insulating properties. Straw, on the other hand, is very similar to wood in terms of its chemical composition, which is why this combination works very well in construction. The so-called equilibrium moisture content of both materials is also between 13-15% by mass. Straw consists mainly of cellulose, lignin and silica. It is covered with a waxy layer which, in combination with the high silicate content, results in a high resistance to moisture. A rotting process therefore only begins after weeks of increased moisture. Even then, a straw bale retains its volume and releases the moisture under its own power, provided the structure allows this. At first, the straws themselves do not absorb moisture at all or hardly at all; it is stored in the air spaces and can also escape again due to the capillary effect. Many insulating materials (mineral wool, etc.) start to clump as soon as a certain moisture content is reached and then release the absorbed water again only with difficulty.

Material properties

Just as settlers in the U.S. at the end of the 19th century were amazed that their buildings constructed with straw bales were still standing years later and used for more than just temporary housing, we are still surprised today by the potential, or rather the multitude of properties in a single building material.


Straw has been used in construction for many thousands of years: 

Straw in bale form has been used in construction only since the invention of the baler about 120 years ago. Straw bales can be used in house construction both in the external walls (insulation, plaster base, static element), as roof, ceiling insulation, but also in the floor slab, provided that we can ensure adequate protection against moisture and condensation.