For the fire to burn, air and combustible material are necessary. Inside the straw bales there are only very small amounts of air as the straw are highly compressed. Straw house walls on both sides are usually plastered. 1.0-1.5 cm thick layer of plaster can withstand fire for half an hour. Under the EU requirements, it is sufficient for people to evacuate.
This is a dwelling house or other building (garage, workshop, farm building, studio, etc.), where the walls are built of straw bales (pressed straw ”bricks” 1m x 0.5 m x 0.4 m dimensions). Small buildings can be built without a frame using just straw bales while in the bigger buildings a wooden or metal frame is needed for the structure and it is filled with straw bales. Straw bales can also be used for roof and floor insulation.
The oldest straw house that is currently in use was built in 1903. It is a home of already third generation of one family.
The longevity of straw buildings highly depends on the straw, their compression and the construction quality. A well built straw house can be used for decades or centuries.
Straw houses are in construction all over world and the practice shows that rodents do not occupy straw houses. In case to avoid the danger of rodents, it is recommended to install a protective metal net at the bottom of the wall ( about 50 cm from the substructure to the top)
The wall of straw bundles is a breathing one. Moisture passes out through such a wall. Seeking to strengthen this effect , the outside wall of the building must be stuccoed with the type of stucco, permeable to moisture and air in order to get natural draught outside. Clay plaster also perfectly absorbs moisture. Straw houses are not damaged by moisture, the walls do not steam up. A steam bath can be build from straw bundles as well. The high relative humidity does not make any damage to the walls of the bath. Due to the breathing , the mould and fungus do not occur on the wall.
”The standard researches in Austria, Denmark, the USA, Germany and other countries define that the ratio λ of the straw resistance of compressed density is 0,045-0,06 W/(m·K)70-150 kg/m3 (the density of small straw bundles- 70-100 kg/m3), if the straw is dry ,and 0,054-0,072 W/(m·K), as the straws are of operational air-dried moisture. Thus, the Heat transmission ratio, evaluating the influence of the wooden framed house, permeable to the heat would be 0,13-0,14 W/(m2·K) (total heat resistance Rt = 7,7-7,1 m2·K/W) of the frame walls, wedged by straw bundles and both sides stuccoed. These results demonstrate that the ratio of the heat( thermal) transmission of the walls is 43-54 % less than normative one, fixed for the walls of the residential buildings UN = 0,2 W/(m2·K) (STR 2.05.01:2005).”
Quoted from the article “The suitability of compressed straw bundles to buildings in construction“ by assoc.professor dr. Vincas Gurskis and assoc.professor dr. Jonas Juodis from Lithuanian University of Agriculture.