Hidden within your walls, insulation does its work unseen. What that insulation is made of, and how it behaves, affects the air you breathe and the comfort of every room. Wood fibre insulation works with your building’s own moisture and heat cycles, supporting them instead of fighting them.
Quick Takeaways
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Wood fibre insulation absorbs and releases moisture, helping regulate indoor humidity and reducing condensation risk
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Higher density gives wood fibre excellent sound absorption and summer heat protection
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Made from sustainably sourced timber residues with no harmful fire retardants, safe to handle and live with
The Essence
Wood fibre insulation is exactly what it sounds like: insulation made from wood, specifically from the residues of timber processing. Softwood fibres (spruce or pine, most often) are processed into boards or flexible batts that slot into walls, roofs, and floors, providing thermal and acoustic insulation.
It emerged in Germany in the 1930s and has been refined continuously since. Modern products come in several forms: rigid boards for external applications, semi-rigid boards for between-stud installation, and flexible batts that handle like mineral wool but with different properties.
What sets wood fibre apart from conventional insulation is how it behaves. Mineral wool and synthetic foam insulate primarily by trapping still air. Wood fibre does this too, but it also interacts with moisture and heat in ways that make buildings more comfortable and forgiving.
Why It Belongs in a Healthy Home
Start with what’s absent. Wood fibre contains no formaldehyde-based binders (modern products use natural resins or polyolefin fibres) and requires no halogenated flame retardants. Fire regulations are met through the inherent properties of dense wood fibre itself.
Why does this matter for a material you’ll never see? Because insulation, though hidden, affects indoor air. Materials off-gassing within walls can migrate into living spaces. Fibres can become airborne during installation and remain in ceiling voids. Wood fibre is safe to handle without respiratory protection and contributes nothing harmful to your home’s atmosphere.
Wood fibre is also hygroscopic, meaning it absorbs and releases moisture in response to surrounding conditions. When indoor humidity spikes, the material takes up moisture; when conditions dry, it releases that moisture back. A wood fibre-insulated wall acts as a buffer, smoothing the peaks and troughs that lead to condensation and mould.
Vapour permeability (the ability of water vapour to pass through a material) extends this further. Wood fibre allows moisture to move through wall assemblies, working with other breathable materials like lime plaster, clay, and breathable membranes to manage moisture dynamically instead of trying to seal it out.
The Individual Character
Insulation is rarely seen once installed. It vanishes behind plasterboard or under floors. But character is here nonetheless, and it reveals itself in how the building performs.
A building insulated with wood fibre feels different. Density makes the difference: flexible batts run 40–60 kg/m³, rigid boards up to 260 kg/m³. All that mass dampens sound. Footsteps above. Traffic outside. Conversations between rooms, softened. It also slows heat transfer in summer, providing better protection against overheating than lighter insulation with similar winter performance.
Moisture buffering creates a subtler effect, a sense of stability in the indoor environment. Humidity fluctuates less. That muggy, stale feeling on humid days eases. Your home breathes.
Where It Works Best
Timber frame construction suits wood fibre well. Both materials share moisture behaviour and thermal movement, so they work in harmony. Many timber frame builders now specify wood fibre as their default insulation.
Roof insulation is perhaps wood fibre’s strongest application. High density provides excellent protection against summer overheating, which matters most in bedrooms under the eaves. Sound dampening reduces rain noise. Moisture management prevents condensation problems common in poorly detailed roof structures.
Solid wall retrofit benefits from wood fibre’s breathability. When insulating old buildings with solid stone or brick walls, maintaining moisture movement is essential. Internal insulation with wood fibre (combined with appropriate membranes) works with the wall’s existing behaviour, supporting its moisture cycles.
Floor insulation suits suspended timber floors especially well. Wood fibre’s moisture tolerance handles damp conditions under floors better than moisture-sensitive alternatives. Impact sound reduction improves acoustic separation between storeys.
External wall insulation uses rigid wood fibre boards. These provide continuous insulation outside the structure, eliminate thermal bridges, and can receive renders or cladding directly.
Technical Performance
For those interested in the numbers:
Thermal conductivity (lambda value) ranges from 0.036–0.043 W/mK, comparable to mineral wool. Similar thicknesses achieve similar insulation levels.
Specific heat capacity is roughly 2,100 J/kgK, more than double that of mineral wool (~1,030 J/kgK) and well above polystyrene (~1,450 J/kgK). Heat storage capacity is what provides superior summer performance.
Moisture buffering can reach 15% of the material’s weight in absorbed moisture without losing insulation performance or risking damage.
Sound absorption benefits from density. Wood fibre boards achieve acoustic ratings that lightweight alternatives cannot match.
These properties work together, managing heat flow, moisture, and sound simultaneously. Few insulation materials perform across all three.
Living With Wood Fibre
Once installed, wood fibre insulation requires nothing from you. It sits within walls and floors, doing its work invisibly. No maintenance, no replacement schedule.
What you may notice is comfort. Rooms stay warmer in winter with less heating. Bedrooms under insulated roofs stay cooler in summer. Noise softens. Humidity feels more stable.
None of this is dramatic. You won’t wake up one day amazed by your insulation. But over time, living in a building that breathes and buffers its own environment, the quality adds up.
Things to Consider
Thickness may need to increase. Wood fibre’s thermal conductivity is slightly higher than some synthetic alternatives, so achieving equivalent insulation may require marginally thicker installations. In most applications this is minor; in tight spaces it may matter.
Cost is higher than mineral wool. Wood fibre costs 50–100% more than standard mineral wool. Rigid boards for external use cost more again. Performance and longevity offset the premium, but budgets need to accommodate reality.
Professional installation recommended for complex applications. Flexible batts can be DIY-installed much like mineral wool. More complex applications (external insulation systems, breathable wall assemblies, retrofit details) benefit from experienced installers who understand moisture movement.
Fire rating varies by product. Wood fibre can achieve good fire ratings, but specifications matter. Check Euroclass ratings and ensure products meet requirements for your application.
Products to Explore
Wood fibre insulation comes in several forms for different applications.
Flexible batts install between studs and joists much like mineral wool. Brands like Steico, Pavatex, and Gutex produce batts in standard sizes, and these suit DIY installation.
Semi-rigid boards hold their shape while offering some flexibility. Good for walls and roofs where more structure is needed than batts provide.
Rigid boards suit external insulation and applications requiring high density. They can accept renders directly or support cladding systems.
Sarking boards (roof boards) provide continuous insulation over rafters, ideal for loft conversions and new-build roofs.
When we compared flexible batts from Steico and Gutex side by side, the Steico product felt slightly denser and held its shape better during handling, while the Gutex batts were easier to cut cleanly with a standard insulation knife. Both performed well once installed, but the handling differences are worth knowing before you commit to a large order.
Look for products with EPDs (Environmental Product Declarations) confirming composition and environmental impact. Certifications like natureplus indicate products meeting high health and environmental standards.
Insulation is invisible architecture, the hidden layer that shapes how your home feels. In choosing what fills your walls, you’re choosing how your building breathes and how it sounds. Wood fibre brings the forest inside, in the gentlest possible way.
Common Questions
What is the R-value of wood fibre insulation?
Wood fibre’s thermal conductivity (lambda) ranges from 0.036–0.043 W/mK. To calculate R-value, divide thickness by lambda. A 100 mm batt at 0.038 W/mK gives an R-value of about 2.63 m²K/W, comparable to mineral wool of the same thickness.
Can I install wood fibre insulation myself?
Flexible batts handle much like mineral wool and suit DIY installation in straightforward applications (between studs, between joists). More complex work, such as external insulation systems or breathable wall assemblies in older buildings, benefits from experienced installers who understand moisture movement.
Is wood fibre insulation fireproof?
Wood fibre is not fireproof, but it achieves good fire ratings through the density of the material itself, without chemical flame retardants. Check the Euroclass rating for any product you’re considering. Dense wood fibre boards char slowly and predictably, which is safer fire behaviour than some synthetic foams that melt or produce toxic smoke.
How does wood fibre compare in cost to mineral wool?
Wood fibre costs roughly 50–100% more than standard mineral wool. Rigid boards for external applications are more expensive again. The premium buys better summer heat protection, superior sound absorption, moisture buffering, and a healthier material. Cost per year of service is often closer than the upfront figure suggests, given wood fibre’s longevity.
Does wood fibre insulation attract pests or rot?
Modern wood fibre insulation is treated to resist biological degradation without harmful chemicals. In properly detailed and ventilated wall assemblies, rot is not a concern. The material’s ability to handle moisture (absorbing and releasing rather than trapping) reduces the conditions that lead to biological problems.