Wood fiber insulation panels - efficient thermal insulation and flexible applications

Wood fiber insulation boards (soft wood fiber boards, softwood fiber boards) are a material for thermal insulation, which offers flexible applications. They have very good thermal insulation and sound insulation properties, but are significantly more expensive than insulation with mineral wool or polystyrene / EPS.

The wood fiber insulation has been in use since the 1930s. Wood fiber insulation panels are among the oldest industrially produced natural insulating materials. They are used for both roof and facade insulation. Their main field of application is the thermal insulation of exterior walls - the panels can be used here for both exterior and interior insulation. Also for partitions in interiors a wood fiber insulation is well suited. Due to their high material strength and their robust surfaces, wood fiber insulation panels are suitable for use in thermal insulation composite systems (ETICS) as well as for ceiling insulation in walkable floors.

Table 1: An overview of the properties of wood fiber insulation boards

thermal conductivityBuilding material classminimum insulation thickness according to EnEV 2014densitysoundproofingPrice per m2
0.04 - 0.055 W / mKB2, E (normal flammable)18 cm150-190 kg / m3depending on use between 34 and 79 dB40 - 50 EUR

How are wood fiber insulation boards produced?

Wood fiber insulation boards consist of 85 percent softwood fibers, which are obtained from sawdust or wood chips. Because of the better fiber quality, softwood is used for their production predominantly. The production of wood fiber boards can be done by wet or dry method:

  • In the wet process, the wood fibers are ground, mixed with water, molded, pressed and then dried at temperatures between 160 and 220° C. Synthetic additives are not essential in this process because the wood-containing lignin acts as a natural binder.
  • In the dry process, wood fibers, optionally textile and corn starch fibers and about 4% PUR resin mixed, sprinkled in the desired thickness and cured by a steam-air mixture. This method can also be used to produce flexible wood fiber insulation panels, which are used, for example, for interspacing or sub-rafter insulation.

Design specifics of the plates

The details of the manufacturing process have an influence on the concrete properties - such as thickness, flexibility, resilience and moisture resistance - of the panels:

  • Thickness: Solid wood fiber insulation boards are usually produced in the wet process in thicknesses between 4 and 25 mm and bonded by means of moisture-resistant adhesives to larger insulation thicknesses. Due to the multi-layer structure, the structural properties of the boards can be optimized, for example by combining layers with different densities. The thickness of dry boards varies between 20 and 240 mm, some manufacturers of wood fiber boards also offer board thicknesses of 300 mm.
  • Flexibility: In the wet process, only solid wood fiber insulation boards are produced, in the dry process also flexible boards can be produced.
  • resilience: The composition of the wood fiber mixture and the consistency of the fibers determine the resilience of the boards - with wood fiber insulation boards, therefore, "customized" insulation solutions are possible.
  • Weather resistance and moisture resistance: External insulation panels must be water-repellent and therefore impregnated with 1 - 2% paraffin. Particularly weather-resistant slabs for roof underlays are made with bitumen or latex additives, with the use of bitumen now plays only a minor role.

In what form are wood fiber insulating boards commercially available?

The panels are available in different thicknesses as rigid, pressure-resistant or flexible insulation panels. In addition to single panels, there are ETICS with wood fiber as well as so-called dry-stitch insulation systems with wood fiber insulation panels for impact sound insulation. Panels for external insulation and ETICS are water-repellent (hydrophobic), with a wood-fiber insulation of internal walls, the hydrophobization may possibly be dispensed with.

Manufacturer of wood fiber insulation boards

Renowned manufacturers of wood fiber insulation are, for example, Agepan, Gutex and Pavatex. Above all, the latter company scores again and again with innovative insulation solutions and products.

Which physical properties do wood fiber insulation panels have?

Wood fiber insulation boards have a thermal conductivity between 0.040 and 0.055 W / mK. Thus, they are superior to the frequently used mineral wool (glass wool, rock wool) and polystyrene / EPS, in the overall spectrum of customary insulation materials they are in the upper midfield. Their high density and fiber structure enable good heat storage and optimal moisture regulation. The sound-insulating effect of wood fiber insulation panels differs according to their field of application. The standard levels of impact sound insulation are 34 decibels (dB), with external wall insulation a value of 56 dB is achieved. Wood fiber insulation panels provide particularly good sound insulation for light interior insulation (up to 62 dB) as well as for beamed ceilings (up to 79 dB).

DIN standards, building material classes, EnEV

Wood fiber insulation boards are classified by the DIN standards 4102-1 and EN-13501-1 as normally flammable materials and thus in the building material classes B2 or E. To the in the current Energy Saving Ordinance (EnEV) prescribed
To achieve heat transfer coefficients of 0.24 W / (m²K), a plate thickness of 18 cm is necessary.

Table 2: Wood fiber insulation panels and other thermal insulation materials in comparison

insulationThermal conductivity (W / mK)Minimum insulation thickness according to EnEV (cm)Cost per m2 (Euro)
Wood fiber insulation boards0,04 – 0,0551840 – 50
glass wool0,032 – 0,0401410 – 20
rock wool0,035 – 0,0401410 – 20
Styrofoam / EPS0,035 – 0,045145 – 20
cellulose0,040 – 0,0451610 – 20
excelsior0,0933680 – 90

Advantages of using wood fiber insulation boards

The advantages of a wood fiber insulation are:

  • Very good insulation properties: Wood fiber insulation panels are in terms of their insulation properties in the upper midfield and are mainly superior to mineral insulation in some cases.
  • Flexible application options: Wood fiber insulation can be used in practically all areas of the building.
  • Excellent heat protection properties: A wood fiber insulation has a high specific heat capacity - to increase the temperature of the material by 1° C, thus comparatively large amounts of heat energy are required.
  • High load capacity and good sound insulation capabilities: Due to the high gross density of the wood fibers, the panels are highly resilient, at the same time resulting in excellent sound insulation properties.
  • Diffusion-open and capillary-active material structure: Wood fiber insulation is capable of absorbing, distributing and removing moisture, which plays an important role especially for roof and interior insulation. As soon as the moisture balance of the building has settled after the insulation has been installed, the formation and evaporation of condensed water balance each other out.
  • Good moisture resistance: The insulating properties of wood fiber insulation boards are only lost if the water content exceeds 20%.
  • Easy installation: There are various methods for fixing wood fiber insulation boards. It is possible to glue the Holzfaserdämmplatten and / or screw.
  • No special recycling procedures: Since the panels are predominantly made of natural materials, there are no special requirements for environmentally friendly disposal. The recycling of residues or disassembly materials is theoretically possible.

Tips & Tricks

With wood fiber insulation panels you decide for a high-quality and flexibly applicable insulating material. A wood fiber insulation is suitable for roofs, facades, storey ceilings and partitions in interiors. In addition, the plates provide optimal sound and heat protection. They are "breathable" and support a good moisture balance in the building envelope.

What are the disadvantages of wood fiber board insulation

Material-related disadvantages do not apply to wood fiber insulation panels. From the consumer's point of view, however, the comparatively high price is likely to have a serious impact on the purchasing decision. Wood fiber insulation panels account for only 1% of the total insulation market, mainly due to the price of 40 to 50 EUR / m2, and 28% of insulation materials, with a market share of 28%, behind the much cheaper cellulose (32%) on the second Space.

For which house areas is a wood fiber insulation in question?

The first "porous fiberboard panels" with a maximum thickness of 20 cm were mainly used as room-side insulation of roof pitches and exterior walls, as wood fiber insulation under parquet and cast asphalt, and as water-repellent "bitumen wood fiberboard" for roof underlays. Since then, the plates and their production processes have been continuously developed, especially in the last 20 years, the application fields for wood fiber insulation panels have greatly expanded. A wooden insulation is possible today in almost all areas of the house. The plates are used for:

  • Roof shortfalls: Here are used hydrophobic - so impregnated - plates.
  • rafter: The wood fiber insulation here consists of a single or multi-layer rigid insulation layer.
  • Intermediate and sub-rafter insulations: The panels for this insulation form can be solid or flexible. In addition to slabs, precisely cut wood fiber insulating wedges are also used here.
  • ETICS for external facade insulation.
  • Wood fiber insulation of exterior walls: For the wood fiber insulation of an exterior wall with a curtain wall, solid or flexible wood fiber boards as well as wooden fiber insulation wedges are used.
  • Heat and sound insulation in interiors: A wood fiber insulation is suitable for all cavity-forming partition wall systems in load-bearing or non-load-bearing design in question, so it is also suitable for the insulation of lightweight partitions in interiors.
  • Airborne and impact sound insulation: For sound absorption, solid or flexible wood fiber insulation boards and wood fiber wedges are placed in the ceiling cavity. Wood fiber footfall sound insulation panels can also be laid "floating" as a ceiling support.
  • Heat / heat protection: Single or multi-layer laid wood fiber insulation panels provide effective heat protection in floor slabs and as floor slabs. Of course, wood insulation is also suitable for the insulation and thermal insulation of the top floor of a house.
  • Flat roof insulation: Also as a material for flat roof insulation, wood fiber insulation panels often have a very noticeable effect on the building due to their heat and sound insulating properties.

What are thermal insulation composite systems (ETICS)?

ETICS are systems with coordinated building materials for the thermal insulation of buildings. The respective insulating material is the core of the system, according to which the plaster and plaster thicknesses used are directed. For example, an ETICS with wood fiber and a mineral plaster results in a diffusion-open wall system, which allows excellent heat and heat protection as well as optimal moisture balance of the building fabric. The wood fiber boards are fixed by adhesive and insulating dowels on the supporting wall. On the plates, a reinforcing layer and a reinforcing fabric are usually applied. The conclusion of the ETICS is given by the exterior plaster.

High construction law requirements for ETICS with wood fiber and other insulating materials

Insulation materials that are used in an ETICS must meet high requirements with regard to their material properties and their fire behavior; the entire systems are tested by the German Institute for Construction Technology. Wood fiber insulation boards are among the materials approved for ETICS, but most systems used in Germany contain mineral wool or polystyrene / EPS as the insulation material. The assembly of a ETICS requires sound technical knowledge, usually they are performed by stucco workers. For self-construction, the systems are not suitable.

Individual building permit and examination

For construction law reasons, all components of the systems including wood fiber insulation must be supplied by the same manufacturer - if this condition is not met, they will de facto be installed illegally. Binding standards do not exist for the systems. Proof of their suitability and usability is provided on an individual basis within the framework of the building inspectorate approval. This regulates the entire application of a ETICS to the façade of a building, including reinforcement materials and fastening systems. Even small deviations from the regulatory content are a shortcoming from a building law perspective.

Plaster wood fiber insulation panels

In a EIFS, the wood fiber insulation also serves as a plaster base. The surface hardness, tensile and compressive strength as well as the surface structure of the panels determine their renderability and the choice of materials for the exterior plaster. The structural properties of the wood fiber insulation boards determine the quality of the plaster coating. The stronger and more stable an insulation is, the better it can be cleaned.

How can wood fiber insulation panels be processed?

In order to cut wood fiber insulation boards, saws with a special serrated edge are suitable. When installing the panels, a ventilation of the wood fiber insulation is to be avoided both in wood frame systems as well as on flat surfaces, which would cause deformations and thus insulation gaps due to different degrees of moisture of the two surfaces. The processing of wood fiber insulation boards may only be carried out in the dry state. Since the plates usually have a circumferential groove and spring, no gaps are created during their installation and installation.

Tips & Tricks

Thermal insulation composite systems (WDSV) with wood fiber enable matched roof and façade constructions in their materials. The systems must be approved by the building authorities and manufactured in all their components by the same manufacturer.