Naturheld Flex Flexible Wood Fibre Insulation is a high-performance, natural and breathable insulation board made from PEFC-certified timber off-cuts, sourced directly from Naturheld’s own sawmill. Only new timber is used, ensuring a consistent, sustainable, and environmentally responsible product. Designed to deliver outstanding thermal performance, acoustic comfort, and moisture regulation, Naturheld Flex is the ideal solution for both heritage renovations and modern low-energy buildings.
With a density of 50 kg/m³, Naturheld Flex is extremely slump-resistant, meaning it fits securely between studs, rafters, and floor joists without sagging over time. This tight fit prevents gaps and thermal leakage, significantly reducing heat loss. With a thermal conductivity of just 0.036 W/mK, it performs on par with or better than most synthetic insulation materials while being fully natural and sustainable.
Unlike many conventional insulation products, Naturheld Flex is both hygroscopic and vapour-permeable. It naturally absorbs and releases moisture, helping to control indoor humidity and prevent condensation, mould growth, and timber decay. This breathability is particularly important in timber frame constructions, roof insulation systems, and historic building upgrades, where moisture management is critical to preserving structural integrity.
Naturheld Flex also provides excellent acoustic insulation, reducing airborne sound transfer through walls, floors, and roofs, while its high specific heat capacity ensures summer overheating protection. By storing heat during the day and releasing it slowly at night, it helps maintain a comfortable indoor climate year-round, keeping homes warmer in winter and cooler in summer.
Key Benefits of Naturheld Flex Wood Fibre Insulation
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Eco-Friendly & Sustainable – Made from renewable, PEFC-certified wood fibres, recyclable and free from harmful additives.
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Excellent Thermal Performance – Low λ-value (0.036 W/mK) ensures energy efficiency and reduced heat loss.
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Breathable & Moisture-Regulating – Vapour-permeable structure (μ ≤ 3) helps prevent condensation and mould.
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Slump Resistant – Dense fibre structure (50 kg/m³) ensures a snug fit without sagging or settling.
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Superior Acoustic Insulation – Absorbs airborne noise for quieter, more comfortable interiors.
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Summer Heat Protection – High thermal mass reduces overheating in lightweight constructions.
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Safe & Easy to Install – Cuts easily with standard tools, skin-friendly, and comfortable to handle.
Applications
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Roof Insulation – Fits securely between rafters, prevents heat loss, and reduces external noise (rain, traffic). Works in combination with Naturheld wood fibre sarking boards for optimal thermal performance.
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Timber Frame Wall Insulation – Provides breathability and prevents moisture build-up, essential for long-lasting timber structures.
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Floor Insulation – Installed between joists to improve both thermal comfort and sound insulation.
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Heritage & Conservation Projects – A natural, breathable insulation ideal for upgrading traditional and historic buildings without trapping moisture.
Technical Features
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Width: 575mm (only available size)
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Density: 50 kg/m³
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Thermal Conductivity (λ-value): 0.036 W/mK
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Thickness: 50mm and 100mm (Other thicknesses available on request)
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Handling: Easy to cut with an insulation knife or saw, skin-friendly, no irritation compared to man-made fibres.
Why Choose Naturheld Flex?
Naturheld Flex is more than just insulation — it is a natural, breathable, and sustainable alternative to synthetic products that often trap moisture and compromise building health. By combining excellent thermal efficiency, acoustic performance, and summer heat protection, it creates healthier, more durable, and more comfortable buildings. Whether you’re insulating a timber frame home, retrofitting a historic property, or upgrading a roof or floor, Naturheld Flex ensures long-lasting performance while reducing your carbon footprint.
