Roundtower SuperTherm is an ultra-lightweight insulating lime plaster designed for breathable internal wall insulation in solid masonry, stone, brick, and heritage buildings. Formulated with hydrated lime, natural pozzolan (metakaolin), and an advanced ultra-lightweight insulating aggregate, SuperTherm delivers exceptionally high thermal performance while remaining fully vapour open and moisture regulating.
Unlike impermeable insulation systems, SuperTherm allows traditional walls to continue absorbing and releasing moisture naturally, reducing the risk of trapped damp, condensation, and mould growth within the structure. This makes it particularly suitable for older solid-wall buildings where maintaining breathability is critical.
Because of its very low thermal conductivity, SuperTherm can achieve significant thermal improvement at relatively thin build-ups compared to conventional lime insulating plasters, while still remaining fully compatible with traditional masonry.
Technical Data
| Property | Value |
|---|---|
| Material | Lime-based insulating plaster |
| Thermal Conductivity (λ) | 0.0395 W/mK |
| Vapour Diffusion Resistance (μ-value) | Approx. 4.2 |
| Density | Approx. 260 kg/m³ |
| Binder | Hydrated lime & metakaolin |
| Aggregate | Ultra-lightweight insulating aggregate |
| Moisture Behaviour | Vapour open & moisture buffering |
| Application Thickness | 30–100 mm typical |
| Maximum Single Pass | Up to 50 mm |
| Fire Performance | Non-combustible mineral composition |
| Finish Coat | Roundtower SuperTherm Finishing Plaster |
Key Benefits
Extremely High Thermal Performance
With a thermal conductivity of λ = 0.0395 W/mK, SuperTherm delivers thermal performance comparable to many insulation boards while remaining a fully mineral, breathable plaster system.
Fully Vapour Open
The low vapour resistance factor (μ ≈ 4.2) allows moisture vapour to diffuse safely through the wall assembly, supporting inward and outward drying of traditional masonry.
Moisture Buffering & Condensation Control
SuperTherm absorbs and rereleases moisture vapour, helping stabilise internal humidity levels and reduce condensation risk on cold walls.
Suitable for Damp & Older Buildings
The plaster is:
- non-organic,
- rot-proof,
- and highly breathable,
making it particularly suitable for:
- solid stone walls,
- heritage buildings,
- and damp-prone interiors.
Lightweight Build-Up
With a density of approximately 260 kg/m³, SuperTherm adds minimal structural loading compared to denser plaster systems.
High Build Application
Can typically be applied in:
- 50 mm coats in a single pass,
- with additional layers applied green-on-green,
allowing faster installation compared to many conventional insulating plasters.
Suitable for Heritage Retrofit
Designed specifically for:
- traditional masonry,
- listed buildings,
- conservation projects,
- and breathable retrofit systems.
Typical Applications
- Internal wall insulation for solid masonry buildings
- Heritage and conservation projects
- Damp and condensation-prone interiors
- Breathable retrofit systems
- Stone and brick walls
- Uneven solid wall insulation
- Low-energy renovation projects
Why Use SuperTherm?
Traditional solid-wall buildings rely on vapour diffusion and capillary drying to manage moisture safely. Impermeable insulation systems such as PIR-backed plasterboard can trap moisture within the wall structure and increase the risk of:
- interstitial condensation,
- mould growth,
- and long-term moisture accumulation.
SuperTherm differs because the entire system remains:
- vapour open,
- moisture regulating,
- and capillary active.
This allows the wall to continue drying naturally while significantly improving thermal performance and internal comfort.
The seamless plaster application also eliminates many of the thermal bridges commonly associated with framed insulation systems.
Thermal Performance
SuperTherm is one of the highest-performing breathable lime insulating plasters currently available.
A typical 50 mm application can improve the thermal performance of a traditional solid wall by over 100% depending on wall type and existing moisture content.
Because wet masonry transfers heat significantly faster than dry masonry, improving vapour permeability and allowing the wall to dry can further improve real-world thermal performance over time.
Installation Overview
1. Surface Preparation
Walls should be stable, clean, and free from:
- gypsum,
- cement contamination,
- paint residues,
- salts,
- or loose material.
2. Background Control
Uneven or highly absorbent substrates may require:
- dampening,
- suction control,
- or bonding preparation prior to application.
3. Plaster Application
SuperTherm can generally be applied:
- up to 50 mm per pass,
- either manually or by suitable plaster spraying equipment.
4. Reinforcement & Finish
The system is typically finished with:
- Roundtower SuperTherm Finishing Plaster,
- mesh reinforcement,
- and breathable mineral or lime finishes.
5. Final Finish
Suitable finishes include:
- limewash,
- mineral paint,
- silicate paint,
- and breathable decorative coatings.
A Breathable Alternative to PIR Drylining Systems
SuperTherm provides a fully mineral, breathable alternative to:
- PIR-backed plasterboard,
- insulated drylining systems,
- and impermeable internal insulation assemblies.
Because the plaster remains vapour open throughout, it:
- supports moisture evaporation,
- reduces condensation risk,
- improves humidity regulation,
- and maintains compatibility with traditional masonry construction.
This makes it particularly suitable for:
- heritage retrofit,
- solid stone buildings,
- and moisture-sensitive low-energy renovations
