Nature Does It Best

Gutex Wood Fiberboard Insulation

Wood you like continuous insulation?


GUTEX 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.

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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.

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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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