November 2, 2017

Nature Does it Best: GUTEX Wood Fiberboard Insulation

 Wood you like continuous insulation?

Gutex_connects_2GUTEX has produced insulating fiberboards from wood for over 85 years. Today, GUTEX is a leader in innovative, environmentally-friendly manufacturing. GUTEX uses a mixture of post-industrial, recycled wood chips and shavings and milled wood that has been harvested and grown using sustainable forestry management practices.

Why Wood?

Wood fiber insulation is a safe, natural and high performing alternative to many synthetic insulation options currently on the market. Wood is a renewable resource and a natural carbon sink. The general recipe for a GUTEX board is 95% spruce/fir wood, 1% paraffin, and 4% PU resin – making it a carbon negative material made from renewable resources that is a great alternative to mineral wool and foam insulation.

As GUTEX says, “nature knows best”, wood has natural vapor open and thermal retention properties that make it the ideal insulation material.

We stock GUTEX products that are suitable for both roof and wall insulation applications. Roll over the products listed above to learn more about the specifics of each and be linked to the product page.

Continuous Insulation and Weather Resistant Barrier (WRB)

The biggest benefit of using GUTEX’s ULTRATHERM and MULTITHERM boards is that you can insulate and weather-proof your assembly in one simple step, cutting labor costs in half. These boards are applied at the exterior, and tongue and groove edges make installation very fast. Because you do not need to line the vertical edges of the boards up with the studs/joists below, you minimize cutting, reduce waste and maximize application speed.

“By adding this board on the exterior, the building is clad, weather and wind protected in one step”

This assembly is watertight thanks to two properties of these boards. The ULTRATHERM and MULTITHERM boards achieve moisture resistance through a hydrophobic treatment of 0.5% paraffin. The tongue and groove assembly also ensures that the boards are immediately waterproof and wind-tight. The building is now protected from the elements during the interior construction phase. The final cladding/roofing should be added within three months.

There are a few remaining details such as valleys, outside corners, dormers, chimneys and windows that need to be additionally waterproofed with tape connections. Simply prime these areas with TESCON Primer RP, and use TESCON VANA 150 to make these connections waterproof and windtight.

Screen Shot 2017-11-02 at 10.25.55 AM

Vapor Open

GUTEX boards are waterproof and vapor open. The paraffin treated boards stop liquid water infiltration, water droplets roll off the boards. The vapor open wood fiber allows the passage of water vapor through the boards, preventing condensation formation in the assembly. GUTEX wood fiberboards are very vapor open, with 44 perm/in, to ensure that your walls can dry out if unforeseen humidity or vapor does enter the assembly. They provide a high drying capability to insulated enclosures, something that is not possible with foam boards. These boards can hold up to 15% of their weight in moisture without losing their insulation capacity, then, when the air is dry, the moisture diffuses out of the assembly. By allowing moisture to escape from and pass through the assembly, you create a safer, more resilient wall assembly that is much less susceptible to mold formation.

Superior Thermal Insulation

Wood has a very low thermal conductivity and a high specific heat capacity, resulting in a material that resists temperature fluctuations. This principle applies in both hot and cold conditions, keeping the assembly warm in cold weather and cool in hot weather. The boards can delay internal temperature rise by 10 or more hours (in combination with dense pack insulation), as shown in this test performed by GUTEX. In contrast, low density materials like foam, mineral wool or fiberglass will heat up rapidly and cannot offer this benefit. 

The time lag- time it takes for heat to reach the interior of the building through the insulation- is 10 hours for GUTEX Thermosafe. On a day where the outside temperature fluctuates by 70 degrees, the indoor air temperature only changes by 5.5 degrees.


Sound Insulation

High densities (from 8.75lbs/CF to 12.5lbs/CF) and tight tongue and groove joints give the boards ideal acoustic properties. Wood fiber can effectively dampen not only airborne sounds from traffic or loud music, but also impact sound caused by construction equipment or heavy footsteps. When installed properly, GUTEX boards can reduce sound levels by 50 dB. Wood fiber is a more effective sound barrier than foam, mineral wool or fiberglass because of its higher density and open porosity. See GUTEX’s sound insulation in action in this video.

When looking for sustainable high-performance continuous insulation solutions, 475 and GUTEX have the answers – with boards in stock now in the US and Canada. Contact us and ask to talk to our resident Gutexpert Aaron McCormack for support on using wood fiber insulation in your next project.


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7 Responses to Nature Does it Best: GUTEX Wood Fiberboard Insulation

  1. Lyka December 9, 2015 at 11:55 pm #

    Hi Foursevenfive,

    Thank you for sharing such an informative article. Keep on posting informative articles. Thanks!

  2. Scott December 29, 2016 at 3:40 am #

    How long has this product been being used in Europe and what can be known about it’s life span?
    How does the product compare price wise to other solutions in use?
    How vulnerable to insects is it?
    When burned does it off gas poison?
    Is there any off gassing?

  3. Floris January 4, 2017 at 11:40 am #

    GUTEXbegan manufacturing insulation boards from ecological wood fibers in 1932.
    Once protected from direct weather exposure (bulk rain water/UV) the product is as durable as any exterior sheathing/high performance WRB.

    In general it is made from 95% spruce/fir wood, 1% paraffin, & 4% PU resin – making it a carbon negative material made from renewable resources that is a great alternative to mineral wool and foam insulation.

    Price wise it can be cost comparable with Mineral wool boards for whole house orders as it avoids the need for a WRB. On roofs, it can be cost effective as well since it can weatherize the building in one step, which can be a significant labor savings.

    Insects:During the production process, the product is heated above 170°C (338°F).
    Such high temperatures dissolve the natural protein in the wood. Therefore the natural occuring protein is no longer available as a nutrient for insects etc.

    SInce starting production, GUTEX has not had any complaints of customers concerning wood pests or rodents settling in its products.

    If GUTEX is exposed to flames, it reacts like any wood. It self chars, which protects the interior against fire/propagation. It does not produce poison, although smoke exposure should be minimized as is the case for all smoke.

    Offgassing: GUTEX is very low in VOC. But since wood naturally contain formaldehydes there minor release from that. However since GUTEX solely used Spruce/Fit which are low formaldehyde wood species, the product does not implicate IAQ as is proven by the NaturePlus certification .

  4. Jim April 18, 2017 at 1:31 pm #

    What is the R value? What thicknesses are available? What is the rot resistance?

    • Floris April 18, 2017 at 3:04 pm #

      R-value of the boards range from 3.9 per inch (THERMOSAFE) to 3.7 for MULTITHERM, 3.4 for ULTRATHERM and 3.1/inch for MULTIPLEX TOP.

      This as a result of the board density going up and the roof- or coverboards having highest densities. As a result we have Architects and builders take advantage of the high R THERMOSAVE, use this in thick (up to 9.25″) and then cover it with a thin layer of MULTIPLEX TOP (or simply use one thick layer of MULTITHERM or ULTRATHERM for faster install)

  5. Mark February 12, 2018 at 11:31 am #

    Does Gutex have the pull out capacity to allow screwing or nailing of siding directly into the material with no strapping required?

    Does Gutex have the shear capacity to replace OSB in a typical assembly?

    • John February 12, 2018 at 4:13 pm #

      GUTEX does the jobs of continuous insulation, vapor-open windtight layer, and weather resistive barrier, but is not a structural replacement for OSB. We have examples of simplified wall systems that we are happy to share with you if you get in touch directly. GUTEX should always include strapping not just for siding, but also to create a proper drainage plane.

      If you would like a system that includes exterior insulation + finish we recommend you check out the GUTEX Thermowall system:

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