Frequently asked questions

About products

• What is wood-fibre board manufactured from?
• How does the process for producing a softwood-fibre board work?
• Are any adhesives or other chemicals used to bond the fibres?
• What is the difference between wood-fibre boards produced by the wet process and the dry process?
• What insulation wood-fibre board thicknesses can be produced?
• Are Hofatex^® wood-fibre boards considered ecologically sound products?
• Are insulation boards safe for the health?
• How are Hofatex^® boards' higher water resistance guaranteed?
• How are Hofatex^® boards protected against wood-destroying insects and pests?

About thermal insulation

• What are the critical features of thermal insulation?
• How is heat conductivity expressed?
• What is the heat transfer coefficient U?
• Are there any values prescribed for thermally protecting buildings?
• How is thermal insulation dependent on thickness and the heat conductivity coefficient (k-value)?
• What is the effect of insulation on heat accumulation?
• What is thermal displacement?
• What is the significance of the insulation's capacity to displace water vapour?
• What is the diffusion resistance factor µ and the equivalent diffusion thickness s_d?
• How does an engineered construction open to diffusion operate?
• How fire resistant are Hofatex^® wood-fibre boards?

About using Hofatex panels

• Where are Hofatex^® insulation boards to be used in constructed framing?
• What has the greater benefits - thermal insulation externally or internally?
• What are heat bridges and how can they be limited?
• What is the advantage of thermally insulating a sloping roof above the rafters?
• How are Hofatex^® panels anchored when acting as thermal insulation above the rafters?
• Does a vapour barrier have to be applied internally?
• Are Hofatex^® Therm insulation panels also suitable for thermal insulation between the rafter beams?
• When using Hofatex^® UD, is it still necessary to use waterproof diffusion foil?
• Do Hofatex^® UD panel seams have to be glued together?
• How long can Hofatex^® UD panels lie exposed on the roof to external weather conditions?
• What are the options for using Hofatex^® panels for supplementary thermal insulation of external enclosure walls?
• How are Hofatex^® panels attached to the outside wall?
• Can wood-fibre boards also be used in hard floors under wet screeds?
• How can Hofatex^® Silent boards be put under floating laminate (parquet) floors?
• What instruments can be used to cut Hofatex^® panels?
• What is the life of the thermal insulation layers made from Hofatex^® boards?

Answers:

What is a wood-fibre board manufactured from?

Only softwood is used in the manufacture of wood-fibre boards. In their production, only wood from sustainably managed domestic sources is used.

How does the process for producing a softwood fibre board work?

Incoming raw wood is cut into smaller "chips", which are the intermediate raw material that is thermo-mechanically broken up in a "defibrator". Next, the fibre is mixed with water and a water suspension is created. This water suspension is heated and drained, forming a fibre carpet that forms the base for the new board. The drained boards are then aired out to attain the final moisture content.

Are any adhesives or other chemicals used to bond the fibres?

No chemicals are used. This type of production uses the wet process, where the action of water and heat reactivates the natural lignin and hemi-cellulose in the wood fibre, ensuring firm bonding.

What is the difference between wood-fibre boards produced by the wet process and the dry process?

The difference is that wood-fibre boards produced by the dry process, as opposed to insulation boards manufactured using the wet-process, require adhesives to be added, most commonly polyurethane-based.

What insulation wood-fibre board thicknesses can be produced?

The wet process only permits the production of basic boards up to 20 mm thick. Thicker boards up to 100 mm are layered with basic boards. Ecologically sound adhesives based on modified natural starch are then used to bond them.

Are Hofatex^® wood-fibre boards considered ecologically sound products?

Yes, they are, from several perspectives from the incoming raw material to the possibility of recycling. The wood used to produce wood-fibre boards is a natural resource that grows again and again and comes from domestic forests which are farmed sustainably. The product itself takes all aspects of the environment into consideration. Hofatex^® insulation panels are fully recyclable. They can be composted or safely burned.

Are insulation boards safe for the health?

Hofatex^® wood-fibre boards include only natural materials which cause no health problems. They are predominantly (up to 98%) comprised of wood fibres. Only natural substances such as paraffin and natural starch are added to improve some of the properties. As opposed to most fibre insulation materials, they contain no carcinogenic formaldehyde.

How is the higher water resistance of Hofatex^® boards guaranteed?

To increase water resistance, a natural hydrophobiser is added to some of the boards (Hofatex^® UD and Hofatex^® System). This is not just a surface treatment; this hydrophobiser is added when the fibre suspension is created, i.e. the entire thickness of the boards have greater water resistance and consequently on both sides.

How are Hofatex^® boards protected against wood-destroying insects and pests?

The wet process for producing Hofatex wood fibre boards removes from the wood all the aromatics which attract insects and pests. Conversely, the final product has an approximately 7-8% humidity content. From a biological point of view, wood-destroying insects are attracted to softwoods with a humidity content of above 15%.

What are the critical features of thermal insulation?

Thermal insulation has to protect the building from heat loss in the winter months (winter heat protection) while also safeguarding the interior against overheating in the summer (summer heat protection). Thermal insulation should likewise work equally well with moisture in the air and water vapour.

How is heat conductivity expressed?

Heat conductivity is a critical property in thermal insulation from the aspect of preventing heat from escaping. It represents the substance's ability to conduct heat and is expressed as a heat conductivity coefficient λ; the lower the value, the more effective the insulation. Most insulating materials have a heat conductivity coefficient around 0.040 W/(m.K).

What is the heat transfer coefficient U?

This is a coefficient which takes into consideration the thermal insulation properties of the constructed building. It expresses the heat flow which is spread throughout the framing and is indicated in W /m. K. It is highly dependent on the heat conductivity of the materials used to construct the building. The lower the value, the less heat loss the building elements cause.

Are there any prescribed values for thermally protecting buildings?

Yes, there are. These values are not uniform. Each country has its own standard heat transfer coefficient values U for sloping roofs, flat roofs, enclosure walls, ceilings, etc. tailored to climatic conditions. In the Slovak Republic, these values are listed in STN 73054 - Thermal Protection of Buildings.

How is thermal insulation dependent on thickness and the heat conductivity coefficient (k-value)?

It follows that the greater the insulation thickness, the lower the heat transfer coefficient U. The table below illustrates the relation between U-values and the thickness of insulation with a heat conductivity of 0.040. Width in mm U W/mK  

Width in mm	U W/mK
20	1.506
40	0.859
60	0.601
80	0.462
100	0.375
200	0.194
300	0.130

What is the effect of insulation on heat accumulation?

The insulation's heat accumulation capacity contributes significantly to the optimal internal climate of buildings, especially during the summer months when internal spaces overheat unpleasantly. If the materials used to construct the building have a greater accumulative capacity, it can effectively inhibit heat fluctuation.

What is thermal displacement?

Temperature displacement is closely related to the construction materials' accumulative capacity, e.g. the highest external afternoon temperatures change in the later hours of the day and at the same time decrease the temperatures inside.

What is the significance of the insulation's capacity to displace water vapour?

Its capacity to displace water vapour (diffusion ability) is a very important property of the thermal insulation material, since a large amount of water vapour is generated inside buildings. Adequate transfer of water vapour throughout the framing is important from the perspective of condensation within the framing. Condensation within the framing constitutes a threat to its useful life.

What is the diffusion resistance factor µ and equivalent diffusion thickness s_d?

The diffusion resistance factor µ indicates how much higher the material's resistance to displace water vapour is than a layer of air with the same thickness and equal temperature. In addition, a traditional coefficient for water vapour diffusion is also the equivalent diffusion thickness s_d, which is the product of the diffusion resistance and the material's thickness and indicates air thickness in metres with the same diffusion resistance as any construction material. Materials with a diffusion factor of up to 10 are considered to have a very high diffusion capability.

How does an engineered construction open to diffusion operate?

It operates on the principle of adequate dispersion of moisture from the internal spaces and their outside layers prevent moisture penetrating from the outside environment. Such framing is at the same time open (vapour barriers do not apply here). The principle of these constructions is to use material where diffusion resistance declines from the inside out.

How fire resistant are Hofatex^® wood-fibre boards?

Under the European harmonised EN 13 501-1 board standard, Hofatex^® wood-fibre boards are classified as easily combustible materials in Reaction to Fire Class E. In accordance with the German DIN 4102 standard, wood-fibres are listed in Flammability Class B2. Fire resistance is the same as other commonly used thermal insulation materials such as polystyrene, polyurethane, etc.

Where are Hofatex^® insulation boards used in constructed framing?

They are widely used in almost all types of engineered framing - roofs, enclosure walls, ceilings and floors.

What has the greater benefits - thermal insulation externally or internally?

The more effective thermal insulation method is to have it on the outside. It is also a safer method from the perspective of possible water vapour condensation. Thermal insulation internally is recommended only in cases when external insulation is not possible. In this case, advice should be sought from an expert.

What are heat bridges and how can they be limited?

Heat bridges are created in places where a thermal insulation layer is in some way disturbed by materials with worse heat conductivity, e.g. the rafter beams in a sloped roof. In the roof, these beams may take up to 20% of the entire area, where wood has a four times worse conductivity than Hofatex^® panels. Heat bridges can be limited by having an adequate insulation layer either above or below the rafter beams.

What is the advantage of thermally insulating a sloping roof above the rafters?

The benefit is that it restricts heat bridges from arising in the area of the rafters. Another advantage of this thermal insulation method is the roof's aesthetic appearance from outside when a wooden insert is used.

How are Hofatex^® panels anchored when thermally insulating above the rafters?

Hofatex^® TopTherm panels together with layers of Hofatex^® UD (or Hofatex Kombi) panels are anchored through the insulation layer by contra-laths to the rafter beams using special screws or nails.

Does a vapour barrier have to be applied internally?

A vapour barrier should prevent water vapour from leaking into the framing (it is mainly applied in roofs). In certain circumstances, the framing can be designed with Hofatex^® panels without using a vapour barrier. This option should be judged by considering each specific framing construction individually, allowing for the actual conditions.

Are Hofatex^® Therm insulation panels also suited for thermal insulation between the rafter beams?

All Hofatex^® projects have a lower level of compressibility. Using them where distances are exactly defined, e.g. between beams or in wooden framing, they must be cut to the precise dimensions. To make the work easier, wedge-shaped Hofatex^® Therm DK panels have been manufactured where only a small part is cut out.

Is it still necessary to use waterproof diffusion foil when using Hofatex^® UD?

Hofafest UD panels are open to diffusion and also have increased resistance to penetrating water. Therefore, they are used as safety hydro-insulation with no need to use diffusion foil. Unlike foil, Hofatex^® UD provides additional thermal insulation and can limit heat bridges in the rafters.

Do Hofatex^® UD panel seams have to be glued together?

Hofatex^® UD panels have a tongue-and-groove at the perimeter which firmly joins the boards together without having to use glue. In roofs with an angle < 20°, the seams are glued together at the surface with butyl rubber or polyethylene Hofatex^® Tape ABK/PE tape.

How long can Hofatex^® UD panels lie exposed on the roof to external weather conditions?

As temporary decking, they can lie exposed to weather conditions for up to three months. In the winter months, they may not be loaded down with snow.

What are the options for using Hofatex^® panels for supplementary thermal insulation of enclosure walls?

They may be used in both ventilated and contact facades to insulate wood-framed or solid enclosure walls.

How are Hofatex^® panels attached to the external wall?

In ventilated facades, the panels are attached through a lath with screws dependent on the base (wood, bricks, cellular concrete, etc.). The wood facade is then fastened to the lath. With contact facades, the panels are first fastened to the enclosure wall and then plaster is applied according to the manufacturer's exact instructions. The panels in both cases are set from the bottom up from a minimum of 30 cm above ground level. The complete Hofatex^® plaster insulation system is available.

Can wood-fibre boards also be used in hard floors under wet screeds?

Yes, they can. All Hofatex^® panels have a high compression strength (min. 30 kPa) and so are particularly suitable as a thermal insulation and soundproofing layer both for dry floors and under wet screeds. They should be separated from wet screeds by hydro-insulation.

How may Hofatex^® Silent boards be put under floating laminate (parquet) floors?

They are laid on the dry base of the flooring vertically. Individual rows are laid one after the other with 2 mm gaps between the boards. A 10 mm dilatation gap needs to be retained for walls and other fixed barriers.

What instruments can be used to cut Hofatex^® panels?

Less thick panels (up to 10 mm) may be cut by a knife. To cut thicker panels, electric tools ordinarily used for cutting wooden materials (circular, ribbon or straight-back saw) can be used. Adequate suctioning should be secured.

What is the life of the thermal insulation layers made from Hofatex^® boards?

High density Hofatex boards have excellent shape retention and, even after many years in place, have not been subject to degradation. These conditions are confirmed by the experience we have gained over 25 years of using wood-fibre boards.