Seagrass (Neptutherm) - the ecological insulation from the sea

Seagrass is an absolutely natural and ecological insulating material. It is vapor-permeable and has very good thermal insulation properties. Another strength of this material is its efficient sound and heat protection.

Seagrass has always been used as a building material and braiding material for everyday objects in the Mediterranean countries. Seagrass for thermal insulation is obtained from the seagrass Posidonia oceanica. Matted root and fiber remains of this aquatic plant - the so-called Neptune Balls - are washed up on many beaches in the Mediterranean Sea. For example, seagrass is imported to Germany from Tunisia and Albania.

From the Neptune ball to the insulating wool Neptutherm

As insulation material for the Central European market, seagrass was "discovered" by the Karlsruhe architecture professor Richard Meyer, who developed the Neptunherm insulation wool from the Neptune balls. Unlike reed insulation, which requires individual building approval, seagrass is generally approved for thermal insulation. A sea grass insulation contains no additives, and boron salts as flame retardants are not required for this natural insulation.

Table 1: Overview of the properties of seagrass insulations

thermal conductivity0.040 - 0.045 W / mK
Building material classAlt: B2, New: E (normally flammable)
minimum insulation thickness according to EnEV 201418 cm
density75 kg / m3
Price per m225 - 35 EUR

How are seagrass insulations made?

The beginnings of modern seagrass insulations were passed in a test: Professor Meyer had a sample of the 2 to 10 cm large Neptune balls examined by the Fraunhofer Institute for Building Physics. The result was that this material has good heat storage capabilities due to its silicate-containing structure, relatively low flammability and is resistant to moisture and mold. For the production of Neptutherm insulating wool, the seagrass balls are cleaned in a mechanical process and comminuted to wool fibers.

How is seagrass used for heat insulation in trade?

Seagrass insulations are only available as loose material. Depending on the fiber size, they are traded and used as stuffing, bulk and injection wool. Theoretically, the use of insulating mats made of seaweed is possible, but currently have no market significance. According to own data, the company Neputherm works on the development of seagrass insulation boards.

Costs and manufacturers of seagrass insulations

With a m2 price of between 25 and 35 euros, Seegras moves in the middle price field of the insulation market. With conventional insulating materials such as stone and glass wool or polystyrene (EPS, XPS), but also with natural materials such as flax and hemp, a building can be significantly better insulated, the advantage of seaweed is in its 100% ecological quality. The only manufacturer of seagrass insulation on the German market is currently Neptutherm. The market share of seagrass in the insulation market is so far very low.

What are the building physics properties of seagrass as an insulating material?

The thermal conductivity (? - lambda) of seagrass is between 0.040 and 0.045 W / mK (watts per meter x Kelvin). Its thermal insulation performance is thus slightly lower compared to mineral wool or polystyrene. However, seagrass insulations enable significantly better sound and heat protection.

Open to diffusion and capillary activity

The water vapor diffusion resistance of seagrass insulations is 1 to 2? - Like other natural insulating materials (eg flax, hemp, reed or coconut fiber), the material is thus highly permeable and capillary-active. With these properties, as well as its extensive moisture resistance, seagrass is particularly suitable for renovation of old buildings.

Table 2: Seaweed and other thermal insulation materials in comparison

insulation materialsThermal conductivity (W / mK)Minimum insulation thickness according to EnEV (cm)Cost per m2 (Euro)
seagrass0,040 – 0,451825 - 35 EUR
reed0,040 – 0,0551810 - 20 EUR
hemp0,04 – 0,0451610 - 27 EUR
flax0,041513 - 30 EUR
rock wool0,035 – 0,0451410 - 20 EUR
EPS / Styrofoam0,035 – 0,045145 - 20 EUR

Application areas of seaweed for thermal insulation

Seagrass insulation has been used almost exclusively in individual home construction. The insulating wool from seaweed is quite versatile. Fields of application of seaweed for thermal insulation are, for example:

  • Facade insulation: Seagrass can be used for both external insulation and internal insulation of exterior walls. An external insulation with seagrass as part of an energetic refurbishment project is described by the company Neptutherm: The entire house initially received a wooden shuttering, the compartments were sealed at the bottom with an OSB board, the seagrass wool was then stuffed manually into the insulation space between the shuttering and wall, Alternatively, use as blow-in insulation is also possible.
  • Roof insulation: Seagrass is used here for temporary rafter insulation.
  • Ceiling and floor insulation: Seabed slurry insulation is ideal for thermal and impact sound insulation of ceilings or floors. The material is used with or without cover also for thermal insulation of the upper floor ceiling.
  • Cavity insulation.
  • Insulation of buildings in wooden frame or wood panel construction.
  • Insulation of prefabricated wooden houses.
  • Heat and sound insulation indoors.

Advantages of seagrass insulations:

  • Poor flammability: Seagrass insulations are classified as "normally flammable" by the building authorities, but do not require any additional flame retardancy, in contrast to other insulating materials for classification in this building material class.
  • Open to diffusion and capillary activity
  • Excellent sound and heat protection
  • High moisture and mold resistance
  • Resistance to pest infestation
  • Easy processing
  • harmful substances
  • Natural disposal, compostability
  • Low primary energy demand for procurement and production: The primary energy requirement of seagrass is at least 30% lower than that of other insulation materials.

Disadvantages of seagrass insulations:

  • The comparatively high price.

Tips & Tricks

Seagrass (Neptutherm) is a natural insulation material that comes on the market exclusively as seaweed wool for bulk, stuffing and insufflation insulations. Seagrass insulations are absolutely free of harmful substances and additives. They are relatively versatile. Due to its highly permeable character, seagrass is particularly well suited for renovation of old buildings. In addition to good insulation performance, the strengths of this insulation material include excellent sound and heat protection.

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