For the insulation of buildings, insulation materials made from polystyrene or mineral wool (glass wool or rock wool) are currently predominantly utilized. They are classified in accordance with DIN 4102-1 (1998) as Building Material Class B1 (“flame-resistant”) and can therefore be used for all building classes. They are, however, non-regenerative and therefore consume finite resources. Insulation materials made from polystyrene can also be harmful to health. Although they are flame-resistant, once the polystyrene has caught fire, it burns with a dense, toxic smoke. Furthermore, it melts and can drip whilst burning.
Wood-fiber insulation materials are a sustainable alternative. They achieve a similarly high insulation effect with the same material thickness and exhibit a non-problematic fire behavior. This means that the mass burn rate is very low, as in the event of a fire, an ash layer forms on the surface which then inhibits the supply of oxygen to the source of the fire and prevents it from spreading rapidly. Compared to polystyrene, significantly fewer toxic smoke gases are created, and wood-fiber insulation materials drip from the façade without burning. However, following the removal of the thermal ignition source, they exhibit the appearance of a glimmer fire. Under unfavorable conditions, this can cause the material to catch fire again at another location in the façade. Wood-fiber insulation materials have therefore been classified as “normal flammability” (Building Material Class 2) until now and are only permitted for Building Classes 4 and 5 with specific approval in individual cases. Our project objective is to develop a special glimmer protection for wood-fiber insulation materials in order for them to be classified as “flame-resistant” in the future and utilized in Building Classes 4 and 5. We are thereby contributing towards increasing the currently comparatively small market share of insulation materials based on renewable raw materials.
Project process
At the Fraunhofer WKI, we manufacture wood fibers and process them into insulation boards. In addition, we simulate the continuous glimmer process and utilize the results in order to derive requirements for a possible glimmer-protection agent. Based on this, we are developing, in collaboration with our project partner, ET Brandschutz GmbH, a glimmer-protection agent for our insulation boards. Various flame retardants are hereby utilized which can be combined in different ways. The aim is to find the right combination in order to safely stop the glimmer process.
We then incorporate the various mixtures of glimmer-protection agents into the manufacture of our insulation boards here at the Fraunhofer WKI. We characterize all developed materials on a specially developed glimmer test bench and on a test bench for determining the tendency of the building product towards continuous smoldering in accordance with DIN EN 16733. As the material to be developed is a type of insulation, we also determine the typical properties of an insulation material (thermal conductivity, raw density profile, water absorption).
In order to ensure that our solution can be economically implemented in industrial production, we are also working together with an insulation-material manufacturer within this project. Gutex Holzfaserplattenwerk GmbH & Co.KG manufactures our material developments on an industrial scale for testing purposes.
Fraunhofer Institute for Wood Research 
