Typha is a very common marsh plant in the western hemisphere, and is the subject of research by the Fraunhofer Institute in Germany. Results show that we may be looking at an exciting, inexpensive and renewable new building material with some very interesting properties.
The plant is known locally by different names. Bulrush and cattail are common in Europe and North America, though bulrush is an ambiguous term; cattail is more specific. We’re sticking to its scientific name, typha latifolia. It turns out to have some very particular characteristics which could be of use to architects and designers around the world.
Typha has frequently been used for filtering sewage water and cleaning up contaminated soil. Its rhizomes have long been known to be edible and its seeds and pulp find application in medicinal compounds. It has historically been used for weaving into baskets and small boats, and now scientists are showing that it may come in handy for a variety of building purposes too.
Researchers with the Fraunhofer Institute, led by Dr. Martin Krus, are exploring ways in which the material could be used in building. Examples that use the bulrush’s great qualities include insulation, structural reinforcement or even a building block. The plant is useful in part because it has adapted to suit the all-round environment of wetlands. It thrives in the damp and the dry, in poor as well as dirty or contaminated soil, in variable temperatures and intermittent light. The plant is resistant to mould and moisture, and its tube-like inner structure is strengthened by a spongy tissue. So the raw plant is suitable for use as a self-supporting insulation material. Its useful biomass has a very low density of around 63 kg/m3.
Taking this idea a step further, the researchers have produced a typha-based insulating panel bound with magnesite. At just 0,052 W/mK, its heat conductivity is very low and it also has great fire-resistance and sound insulation. Experiments are ongoing to find out how well the material performs in a full-scale building. The developers hope to introduce the panels into the building industry, as they state that no manufacturer has yet taken it upon themselves to mass-produce the panels. Considering that typha is a hardy, fast-growing and easy to harvest crop with a very wide reach, the first problem – that of availability – has already been overcome.
Processing the plant is relatively simple too. Leaves are cut horizontally into strips around 7 cm long. Next, they are sprayed with eco-friendly mineral adhesive and then heated and pressed. The panel can then be shaped for use as insulation, sandwich panelling or a light-weight construction component. There are currently several companies specialising in building with typha. They stress the extremely environmentally friendly aspects of the product. The plant grows at speeds of about four times those of wood, meaning more useable material more quickly – and less strain on the world’s trees.
At the end of its effective life-time, the typha panel can be recycled or composted, which closes a very neat and plausible circle in sustainable building.
More information here.