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ISOCALM: Thermal insulation boards made of elephant grass

Constructing buildings with renewable resources is becoming more and more trendy. The Schorndorf-based company ISOCALM GmbH specialises in the manufacture of thermal insulation boards made of elephant grass. The elephant grass is grown and processed in Africa and global distribution of the boards is organised through the company's headquarters in Germany. The ISOCALM boards can be used as a base for plaster as well as for internal and external thermal insulation.

Napier grass or elephant grass (Latin "Pennisetum purpureum") has long been used in Africa as an insulation material. © ISOCALM GmbH

Elephant grass, which is a term used for numerous savannah grass species, is the favourite forage plant for elephants, hence the name. ISOCALM boards are made of grass from the Pennisetum purpureum species, also known as Napier grass. It belongs to the family of sweet grasses. The grass is native to the subtropical zone of southern Africa, Zimbabwe to be more precise.1 It can withstand short droughts and thrives particularly well in areas with high annual precipitation. Up until now, Napier grass has usually been left behind on crop fields, and burned. The grass grows wild on peanut fields, amongst other places. It can grow up to two metres high. Due to its high yield, fresh green grass is used as cattle forage; dry grass can be used to produce biofuel.2 Green elephant grass functions as an insect trap, which is why it has been used to combat pests like the North American stem borer using an environmentally friendly method called push-pull.1 In tropical regions, the grass has long been used for making roofs. Reed grasses were already used in Antiquity as insulation material.

The idea of ISOCALM is born

Karl Schock (83), a retired engineer, developed the ISOCALM project. © ISOCALM GmbH

Twenty-one years ago, Karl Schock, engineer and developer of the ISOCALM insulation boards, established the foundation Opportunity International Germany whose goal was to reduce poverty. He was awarded the German Federal Cross of Merit in 1999 for his commitment based on his Social-Christian beliefs.

In 2012, on a trip to Gambia in West Africa, Karl Schock, engineer and CEO of ISOCALM GmbH, noticed the large number of young people with no work, no prospective in life and only one goal in mind: fleeing to Europe. The West African landscape is characterised by wide Napier grass savannahs. That’s what gave Karl Schock the idea of using this wild, fast-growing grass to produce bioecological thermal insulation boards for use in natural houses. Up until then, it had either been used as cattle feed or just left where it grew. “I was looking to create jobs that effectively counteracted migration and generated high added value products that the country could export,” said Schock. “It took me five years to turn the idea into a product, as the authorities in Africa and Germany were not very cooperative,” Schock explained.

He called his insulation boards ISOCALM. The term is a combination of the word “insulation” (German: Isolation) and the Latin word “calamus” meaning reed or straw. ISOCALM is a so-called corporate social responsibility (SCR) project. This means that future surplus will flow directly into jobs and social development. In Germany, the demand for renewable building materials continues to rise.

Processing elephant grass into insulation boards

Edu stitching the grass together - this is how the ISOCALM board is stitched together with jute yarn in a press frame. The process is totally CO2 neutral. © ISOCALM GmbH

The elephant grass boards are manufactured by hand in Gambia using a simple technique adapted to local conditions. The process undergoes quality control by the German company before the insulation boards are packed into containers and transported to Europe. The entire production process from growth to transport is CO2 neutral.

If Napier grass is not harvested or used as animal feed, the seeds fall out and the grass lignifies. As a result, it can no longer be used as cattle feed. Making insulation boards is therefore not in competition with the use of the grass as animal feed. The Napier grass is harvested by locals by hand and transported in donkey carts to the processing area where it is cut into appropriate lengths and stacked in even layers. The thickness of the ISOCALM boards can be varied according to customers’ requirements. Care is taken to ensure that the grass in each individual board is the same compactness. The compacted grass is then packed into a swivel frame and stitched together with strong jute yarn, leaving ten centimetres between each stitch. The knots on the yarn appear on alternating sides of the board, and glue is applied to prevent the boards from disintegrating when they are cut. The boards are subsequently removed from the press frame and cut evenly. At present, 12 workers are able to produce around 4,000 square metres of insulation boards per year. As sales increase, the company hopes to increase production capacity and thus the number of employees and harvesters.

Napier grass has many valuable characteristics

Unlike reeds, elephant grass does not grow straight, but has branches and knots. As a result, rather than lying in one direction side by side in the ISOCALM boards, the stalks become felted. This results in relatively lightweight, adaptable insulation boards that can easily be cut to size. Using jute yarn rather than metal wire also contributes to this characteristic. As elephant grass is hollow, it can store heat very well. The elephant grass insulation boards are open to diffusion, and are therefore ideal for use in rooms in which humidity exchange needs to take place. The boards can store water molecules and gradually release them into the environment, thus controlling the indoor climate.3

Napier grass is basically resistant to microbes. However, because it is a natural material, if it is exposed to humid conditions (outer wall) for a long time, it may become infested with mould or microbes. Therefore, care needs to be taken that the humidity can dry off again (breathing walls), something that can easily be achieved by way of diffusion. “ISOCALM is chemical-free, 100% biological, and when combined with clay or mortar, can reach up to F30 in terms of fire resistance class,” said Schock.

ISOCALM is already used successfully

Napier grass is mainly combined with clay and mortar in a wet-on-wet procedure. © ISOCALM GmbH

ISOCALM is very well suited for the energy renovation of internal and external walls of old buildings. It is used in dry construction systems, for floor and roof insulation and as infill material for beam constructions. ISOCALM is perfect for footfall sound insulation in ceilings. When used for insulating external walls, ISOCALM boards are plastered over. However, it is recommended that additional structural wall supports are installed. The insulation boards are not only used for wall insulation, but can also be used as a plaster base, e.g. as external plaster with lime.

ISOCALM boards are usually attached wet-on-wet with clay. They are pressed onto a layer of mortar spread over the wall. When used as external wall insulation, the boards are either nailed down or doweled. Due to the special structure of the Napier grass, the boards are also suitable for application on uneven surfaces. The boards can also be combined nicely with a wall heating system where the copper pipes are attached to the jute yarn using cable straps. When used for timber stud constructions, it is advisable to install both core and external insulation to prevent a thermal bridge.

In 2015, the company refurbished a building called “DasNaturhaus”, a listed 17th-century building in the city of Schorndorf. ISOCALM insulation boards were used to insulate the internal walls as the façade had to be preserved. There are plans to use ISOCALM boards in Gambia for insulating external walls to protect against the heat.

According to the German Bioeconomy Council, the construction industry is "largely determined by the costs of renewable building materials relative to fossil alternatives (such as insulating materials)"4 (p. 48). Sustainable building construction can only be successful if a legal framework (ordinances or laws) is implemented. These in turn will only be introduced when there is greater public awareness about sustainability.4 "The demand for renewable building materials is high, but many good products are not yet well-known enough. Therefore, we are still putting a lot of energy into convincing consumers about the positive qualities of the insulation boards and establishing ISOCALM on the market," says Karl Schock.

Schock is optimistic about the future. He has already invested in a first production hall in Gambia and would like to create 100 permanent jobs for locals as well as offer seasonal harvest work in the near future.


1 https://www.biologie-seite.de/Biologie/Napiergras

2 https://de.wikipedia.org/wiki/Napiergras

3 https://www.haus.de/bauen/diffusionsoffen-was-heisst-das

4 Zinke, H., El-Chichakli, B., Dieckhoff, P., Wydra, S., Hüsing, B.: Bioökonomie für die 
  Industrienation. Ausgangslage für biobasierte Innovationen in Deutschland verbessern, 
  December 2016



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