Improve thermal comfort and energy efficiency in traditional buildings with Roundtower Lime’s range of breathable solid wall insulation systems. Designed specifically for solid masonry walls, our solutions balance thermal performance, vapour permeability, and heritage compatibility—essential for older buildings where conventional insulation can trap moisture and cause long-term damage.
We supply a curated selection of natural, breathable insulation materials ideal for internal solid wall insulation:
Roundtower SuperTherm – Insulating Lime Plaster
A revolutionary insulating lime plaster with a thermal conductivity of 0.039 W/mK, SuperTherm is applied in layers up to 50mm in one coat. It offers three times the insulating value of traditional lime-based plasters, while remaining highly vapour open (μ = 4.2). SuperTherm is ideal for heritage renovations where breathability, insulation, and moisture buffering are critical.
Roundtower Lime Insulating Plaster
Made with NHL 2 and lightweight aggregates, this insulating plaster offers a K-value of 0.12 W/mK. It’s easy to apply directly to solid walls and provides a cost-effective, conservation-friendly insulation option, particularly for curved or uneven surfaces.
Cork Board Insulation
Our 100% natural expanded cork boards (λ = 0.036–0.040 W/mK) are ideal for internal wall insulation where sustainability, acoustic absorption, and fire safety are priorities. Fully breathable, chemical-free, and rot-resistant, cork boards are bonded to the wall and finished with a lime-based render or skim coat.
Calcium Silicate Boards (e.g., SkamoWall)
Highly effective at preventing mould and buffering internal humidity, calcium silicate boards are perfect for insulating solid walls prone to condensation or rising damp. With excellent capillarity and vapour permeability, they offer insulation while supporting healthier indoor air quality.
Wood Fibre
Wood Fibre Boards are an excellent natural insulation choice for breathable construction, offering a combination of thermal efficiency, moisture regulation, and eco-friendly performance. Made from compressed softwood shavings, these boards are ideal for internal solid wall insulation, roofing systems, or external wall systems (as part of a breathable render system).
At Roundtower Lime, we supply Steico wood fibre boards, known for their vapour-open structure, thermal conductivity as low as 0.038 W/m·K, and excellent acoustic insulation properties.
Wood Wool Boards
Wood Wool Boards (CE Woodwool) are high-performance, cement-bonded insulation boards made from long wood fibres bound with mineral binders. They combine excellent thermal and acoustic insulation and high compressive strength, making them suitable for both internal wall insulation and as a direct render carrier board.
Benefits of Roundtower Solid Wall Insulation Systems
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Designed for solid masonry – lime, stone, brick, cob
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Breathable & vapour open – reduces condensation risk
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Natural & sustainable materials – cork, lime, wood fibre, silicates
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Ideal for conservation projects – reversible, compatible with heritage finishes
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Improves thermal comfort – reduces cold spots, stabilises internal temps
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Moisture-buffering – helps regulate humidity and prevent mould
Frequently Asked Questions (FAQ)
Q1: Why is breathability important in solid wall insulation?
A: Solid masonry walls need to "breathe" to release moisture naturally. Vapour-permeable insulation prevents trapped damp, which can lead to condensation, mould, and structural damage. All our insulation systems are designed to support this natural movement of moisture.
Q2: What’s the best insulation option for uneven stone walls?
A: Roundtower Lime Insulating Plaster or SuperTherm are ideal, as they can be applied directly to irregular surfaces without the need for battening or framing. They also eliminate cold bridging by creating a continuous thermal layer.
Q3: Can I apply lime plaster directly on insulation boards like Wood Fibre or Calcium Silicate?
A: Yes. Wood Fibre boards are usually rendered with breathable lime plasters like Roundtower Board Render + Heritage Lime Skim, while calcium silicate boards can be finished with Skamol Smooth Plaster or Skamol Lime Mortar, depending on the desired texture and breathability requirements.
Q4: Can I still use mineral paint finishes like Beeck after insulating?
A: Absolutely. We recommend Beeck Maxil Pro for internal walls. These mineral paints are vapour-permeable and compatible with all Roundtower insulation systems.
