Hidden within your walls, insulation does its work unseen. But what that insulation is made of — and how it behaves — affects the air you breathe, the moisture in your home, and the comfort of every room. Wood fibre insulation offers an alternative that works with your building, not against it.
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 than synthetic alternatives 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 (typically spruce or pine) are processed into boards or flexible batts that slot into walls, roofs, and floors, providing thermal and acoustic insulation.
The material emerged in Germany in the 1930s and has been refined continuously since. Modern wood fibre insulation comes in various forms: rigid boards for external applications, semi-rigid boards for between-stud installation, and flexible batts that handle like mineral wool but with fundamentally different properties.
What distinguishes wood fibre from conventional insulation isn’t just what it’s made of — it’s 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
The air quality case for wood fibre begins with what’s absent. Unlike some synthetic insulation, wood fibre contains no formaldehyde-based binders (modern products use natural resins or polyolefin fibres) and requires no halogenated flame retardants. The material passes fire regulations through the inherent properties of dense wood fibre, not chemical treatment.
This matters 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 insulation is safe to handle without respiratory protection and contributes nothing harmful to your home’s atmosphere.
The hygroscopic nature of wood fibre provides active benefit. The material can absorb significant moisture from surrounding air when humidity is high, and release it when conditions change. A wood fibre-insulated wall acts as a moisture buffer, smoothing the peaks and troughs that can cause condensation, mould, and structural problems.
This breathability extends to vapour permeability. Wood fibre allows water vapour to pass through, working with other breathable materials (lime plaster, clay, breathable membranes) to create wall assemblies that manage moisture dynamically rather than attempting to seal it out entirely.
The Individual Character
Insulation is rarely seen once installed — it vanishes behind plasterboard or under floors. But there is character here nonetheless, and it reveals itself in performance rather than appearance.
A building insulated with wood fibre feels different. The high density (typically 40-60 kg/m³ for flexible batts, up to 260 kg/m³ for rigid boards) provides mass that synthetic alternatives lack. This mass dampens sound transmission — footsteps above, traffic outside, conversations between rooms. It also slows heat transfer in summer, providing better protection against overheating than lighter insulation with similar winter performance.
The moisture buffering creates a subtler difference — a sense of stability in the indoor environment. Humidity fluctuates less dramatically. That muggy, stale feeling on humid days is less pronounced. The home breathes.
Where It Works Best
Timber frame construction suits wood fibre naturally. The material works in harmony with structural timber, matching its moisture behaviour and thermal movement. Many timber frame builders now specify wood fibre as their default insulation.
Roof insulation is perhaps wood fibre’s strongest application. The high density provides excellent protection against summer overheating — critical in bedrooms under the eaves. Sound dampening reduces rain noise on roofs. Moisture management prevents the 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 natural behaviour rather than fighting it.
Floor insulation suits suspended timber floors particularly well. Wood fibre’s moisture tolerance handles the damp conditions under floors better than moisture-sensitive alternatives. Impact sound reduction improves acoustic separation between floors.
External wall insulation uses rigid wood fibre boards. These provide continuous insulation outside the structure, eliminating thermal bridges, and can receive renders or cladding directly.
Technical Performance
For those interested in numbers, wood fibre performs well on the metrics that matter:
- Thermal conductivity (lambda value) typically ranges from 0.036-0.043 W/mK — comparable to mineral wool, meaning similar thicknesses achieve similar insulation levels.
- Specific heat capacity is roughly 2100 J/kgK — significantly higher than mineral wool (~1030 J/kgK) or polystyrene (~1450 J/kgK). This high capacity to store heat is what provides superior summer performance.
- Moisture buffering capacity 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 performance ratings that lightweight alternatives cannot match.
These properties combine to create insulation that works harder than simpler alternatives — managing heat flow, moisture movement, and sound transmission simultaneously.
Living With Wood Fibre
Once installed, wood fibre insulation requires nothing from you. It sits within walls, roofs, and floors, doing its work invisibly. There’s no maintenance, no replacement schedule, no interventions needed.
What you may notice is comfort. Rooms stay warmer in winter with less heating. Bedrooms under insulated roofs stay cooler in summer. Noise from outside, from upstairs, from adjacent rooms — all somewhat muted. Humidity feels more stable.
These aren’t dramatic effects. You won’t wake up one day amazed by your insulation. But over time, living in a building that breathes, that buffers, that manages its environment — this quality of habitation adds up.
Things to Consider
Thickness may need to increase. Because wood fibre’s thermal conductivity is slightly higher than some synthetic alternatives, 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 typically costs 50-100% more than standard mineral wool. Rigid boards for external use cost more again. This is offset by longevity, performance, and health benefits, but budgets need to accommodate reality.
Professional installation recommended for complex applications. While 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. These suit DIY installation and standard construction.
- Semi-rigid boards hold their shape while offering some flexibility. These work for walls and roofs where more structure is needed than batts provide.
- Rigid boards suit external insulation and applications requiring high density. These 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 where maximum space and performance are wanted.
Look for products with EPDs (Environmental Product Declarations) confirming composition and impact. Certifications like natureplus indicate products meeting high environmental and health 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, how it sounds, how it responds to the seasons. Wood fibre brings the forest inside, in the gentlest possible way.