FAQ

Is the straw house resistant to fire?

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, this is sufficient for people to evacuate. Tests of similar constructions have achieved fire resistance of up to 120 minutes!

Video from german and czech fire experiment

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Are houses built using straw long-lasting?

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 use of dry straw, protection against moisture during building, their compression and the construction quality. A well built straw house can be used for decades or centuries.

Are rodents dangerous to straw houses?

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)

How does moisture affect straw and does mould or fungus occur?

Walls made form straw panels iare „breathing“, that is: lets moisture pass to the outside. Seeking to strengthen this effect, the outside wall of the building must be permeable to moisture (special plaster or ventilated facade) but preferrably airtight, because otherwise the draft of air could create moisture buildup. Clay plaster on the inside also perfectly absorbs moisture and regulates the interior air humidity. Straw houses are not damaged even by high moisture contents in for example bathrooms. A steam bath can be build from straw panels as well, as the inside surface temperature is so high to avoid condensation. Due to the high inside surface temperatures and avoidance of thermal bridges, mould and fungus can not occur on the wall.

What is the thermal resistance of the straw wall?

The standard researches in Austria, Denmark, the USA, Germany and other countries define the ratio λ (lambda value) for compressed straw in the region of 0,045-0,06 W/(mK), depending on density and orientation of straw. Austria uses the λ value of 0,050 W/(mK), the Germans he λ value of 0,052 W/(mK). These include a safety margin for natural materials. We use for our calculations a very safe value of 0,056W/(mK) for straw. The resulting U-value for a 400mm thick straw wall would be 0,14 W/(m2K) and the equivalent resistance R= 7,1 m2K/W. Combined with a woodfibre board on the outside we can achieve a U-value as low as 0,10 W/(m2K) (R=10 m2K/W) for the whole wall construction, wooden construction included.