The Roundtower Internal Wood Fibre Board System is a complete, breathable insulation solution designed specifically for solid masonry walls in both historic and contemporary buildings. Built around Steico Internal wood fibre boards, this system improves thermal performance while maintaining full vapour permeability — critical for managing moisture in older structures.
Ideal for retrofitting solid wall properties, this internal insulation system offers a natural, sustainable alternative to synthetic insulation boards, while supporting healthy indoor air quality and preserving the breathability of traditional building fabric.
System Overview
The system begins with the application of Steico Internal wood fibre boards directly onto a levelled wall surface. These high-density, rigid boards are capillary-active and designed to buffer moisture while delivering high insulation performance. They are then finished with a breathable lime or silicate render such as Roundtower Board Render and an internal top coat (e.g., Heritage Lime Skim or BreathAplasta Smooth).
Key Benefits
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Fully Breathable System – Supports moisture buffering, reducing condensation risks
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High Thermal Performance – λ = 0.038 W/m·K, improving energy efficiency
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Healthy Indoor Environment – Regulates humidity and contains no harmful chemicals
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Sustainable Materials – Made from FSC-certified wood with minimal embodied carbon
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Improved Occupant Comfort – Warmer internal surfaces, better acoustic insulation
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Ideal for Heritage Buildings – Suitable for use in protected structures and conservation areas
Applications
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Internal wall insulation on solid stone or brick walls
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Suitable for heritage retrofits, period homes, or energy upgrades where vapour control is critical
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Can be used in conjunction with breathable base coats like Roundtower Lime Insulating Plaster or Tector Natural Base
FAQs – Internal Wood Fibre System
Do the walls need to be level before installation?
Yes. Uneven or rough walls should be levelled using a vapour-open levelling plaster such as Roundtower Insulating Plaster or Tector Natural Base.
Can wood fibre boards trap moisture?
No. Steico Internal boards are capillary-active, allowing moisture to be safely buffered and released over time, which reduces interstitial condensation risks.
What is the typical board thickness used internally?
Common thicknesses range from 40mm to 100mm, depending on available space and target U-values.
Can I use a vapour control layer with this system?
No, a vapour control layer is not needed. This system is designed to be fully vapour open, allowing the wall to dry inward naturally.
What finish can I apply?
You can finish the system with Roundtower Board Render + Heritage Lime Skim and use Beeck Maxil Pro for a scrub-resistant, breathable paint finish.
