Cattails — Typha sp — are a very useful material, one that can be effectively employed for a variety of very different purposes. Throughout history, they have served as a nutritious food source, a source of downy material for bedding, a raw material for wickerwork, a means of cleaning wastewater at sewage treatment plants and of removing toxins from soils, and as a medicinal plant. And now, researchers at the Fraunhofer Institute for Building Physics IBP in Valley have identified the material as one that possesses great potential as a construction material, particularly with regards to use as insulation.
Dr. Martin Krus, Head of Test Center at IBP, explains: “As one of nature’s swamp plants, cattails are resistant to molds and are very well equipped to deal with moisture. The leaves of the plant have a fiber-reinforced supporting tissue that is filled up with a soft sponge tissue. Through this special construction, they are extraordinarily stable and possess an excellent insulating effect. This effect is also preserved in the finished products.”
The researchers — working in consultation with partner typha technik Naturbaustoffe — have created a potentially commercially-viable magnesite-bound insulation panel composed of cattails. The new panel design possesses a low heat conductivity of 0.052 W/mK (watts per meter and Kelvin) and also effective fireproofing, soundproofing, and heat insulation; as well as being relatively permeable, but still tight enough to make a vapor control barrier unnecessary for most purposes. The material is also able to cope with high pressure parallel to the panel surface.
The impressive qualities of the new cattail panels were validated by the researchers during a 1.5-year-long experiment conducted using a traditional half-timbered home in Nuremberg. The outer walls and timber work of the home were retrofitted with the Typha panels. “The local craftsmen were enthused by this sustainable material,” says Krus.
Even though cattails can be utilized to create impressive construction materials, they have yet to exploited on the industrial scale.
“Cattails are highly prolific, especially in East Europe — mainly Romania and Hungary. The wetland plant is not being cultivated in this part of the world, so it would have to be imported extra,” Krus says, also noting that there are regions in Germany that would be suitable areas for cultivation — in particular, dried out lowland moors that were once used for agricultural purposes but are now unused.
Krus also notes: “Drained lowland moors are a source of CO2 emissions. Each year, up to 40 million tons of carbon dioxide are released in Germany by draining.” That’s a substantial amount — as a comparison, automobile use in Germany results in the release of about 105 million tons of CO2 every year. Those emissions could be entirely prevented, though, simply by cultivating cattails. And it’s also worth noting that such lowland moors are home to many rare animals and plants — stemming their destruction greatly benefits such species.
It’s also worth mentioning that cattails grow extremely fast, meaning that high yields are to be expected. When combined with the ease of processing, such high yields could make the cultivation of cattails very profitable for those involved. “The plant can be processed easily,” Krus emphasizes.
The Fraunhofer news release gets into the specifics of the process:
The leaves are detached horizontally into rod-like particles and then shortened at the correct length of around seven centimeters. Next, they are sprayed in a drum with environmentally-sound mineral adhesives and brought into a heated press. Currently, this process is performed manually. The expert and his colleagues have not yet found a manufacturer willing to undertake serial production of the panels.
“Certainly the typha panel would be extraordinarily competitive if they were produced in a series production process,” Krus states.
As the material possesses so many impressive technical properties, and also complete recyclability into the materials cycle, it could potentially be used for a wide range of different purposes. “Because of the high flexural rigidity and simultaneously low weight, the material can be used for roof construction or as a lightweight sandwich element for flooring and intermediate ceilings. It can also be used to design door leafs, window and door lintels; it is likewise possible to replace timber beams.” The researchers also note that plaster can be effectively reinforced with the use of the cattail’s seed parachutes, via the mixing of the seed parachutes directly into the lime plaster — thus preventing the formation of fissures in the material.
“In principle, one could build an entire building out of Typha, if one excludes pipes, windows and the roofing,” says Krus.