Roxul exterior insulation is a rock wool-based solution designed to improve thermal performance and protect building facades from weather extremes. This system combines mineral wool core with a fiber reinforced composite finish that resists moisture, mold, and fire while supporting long term durability.
Engineered for both new construction and retrofit applications, roxul exterior insulation integrates with cladding, air barriers, and drainage layers to create a robust envelope strategy. Specifications, installation details, and local code compliance should always be verified with project specific design guidance.
| Product | Thermal Conductivity | Fire Performance | Water Absorption |
|---|---|---|---|
| Roxul Comfortboard 80 | 0.040 W/mK | Non-combustible A1 | Low, vapour open |
| Roxul Comfortboard 100 | 0.041 W/mK | Non-combustible A1 | Low, vapour open |
| Roxul Stone Wool Board | 0.040 W/mK | Non-combustible A1 | Low, vapour open |
| Roxul Safeboard | 0.047 W/mK | Non-combustible A1 | Low, vapour open |
Thermal Performance and U Value Range
How Roxul Exterior Insulation Reduces Heat Loss
Rock wool boards used in roxul exterior insulation deliver low thermal conductivity, which minimizes heat transfer through walls. Higher compressive strength helps maintain cavity space and prevents insulation settling over time, supporting steady thermal resistance.
R Value and Thickness Options
Available in multiple thicknesses, roxul exterior insulation allows designers to meet target U values without excessive wall depth. Typical configurations can achieve low U values suitable for passive house and energy code requirements in various climate zones.
Moisture Control and Air Barrier Integration
Vapour Open Structure
Roxul exterior insulation is vapour open, allowing drying toward the outside if moisture occurs within the assembly. This behaviour helps protect cladding fasteners and sheathing by reducing prolonged high humidity inside the wall cavity.
Combined Air Barrier Strategies
When paired with continuous air barrier membranes, roxul exterior insulation limits convective heat loss and reduces risk of interstitial condensation. Detailing around windows, balconies, and penetrations is critical to maintain continuity and control moisture entry paths.
Fire Safety and Regulatory Compliance
Non Combustible Material Class
Roxul exterior insulation is classified as non-combustible with Euroclass A1 and US ASTM E136 ratings. This performance supports approvals in high fire risk zones and multi story applications where stringent fire testing is required.
Impact on Occupant Safety and System Design
Mineral wool core maintains structural integrity under high temperatures, which can contribute to escape routes and firefighting operations. Designers should coordinate with local authorities and follow tested details for compliant facade systems.
Facade Durability and Installation Approaches
Mechanical Fixing and Load Resistance
Roxul exterior insulation boards can be mechanically fixed with corrosion resistant anchors into substrate or supporting structures. Compressive strength and dimensional stability help anchors perform consistently under wind loads and thermal cycling.
Cladding Attachment and Detailing
Insulation thickness and fastener spacing are considered when selecting claddings, including brick, metal panel, and timber treatments. Proper flashing, drip edges, and perimeter seals address bulk water intrusion and support long term facade durability.
Key Takeaways for Project Planning
- Verify local code and fire regulation requirements for specific thickness, finishing, and anchorage criteria.
- Design continuous air and water management layers to work with the vapour open characteristics of roxul exterior insulation.
- Select appropriate anchor types and spacing based on substrate, cladding load, and expected wind forces.
- Plan details at balconies, junctions, and penetrations to limit thermal bridging and moisture accumulation.
- Coordinate scheduling for installation sequencing so insulation, barriers, and cladding are installed in a protected, dry condition.
FAQ
Reader questions
Can roxul exterior insulation be used in a renovated building without changing the cladding?
Yes, roxul exterior insulation can often be installed externally during a renovation while retaining the existing cladding, provided sufficient anchorage and substrate conditions are verified and detailed to manage thermal bridging and moisture.
What are the expected performance differences between wood fibre and roxul exterior insulation in the same wall system?
Roxul exterior insulation typically provides higher compressive strength and lower water absorption than wood fibre, which can improve resistance to cladding loads and drying capability under wet conditions, though wood fibre may offer higher vapour permeability depending on product selection.
How does roxul exterior insulation affect the fire rating of a facade?
By using non-combustible mineral wool boards, roxul exterior insulation contributes to a facade assembly with improved fire resistance and limited flame spread, enabling designers to meet strict building code requirements for fire separation and occupant safety.
What maintenance and inspection practices are recommended for roxul exterior insulation systems?
Inspection of fasteners, seals, and drainage details at least annually, plus after extreme weather events, helps identify issues such as cladding deflection, water staining, or anchor corrosion early and supports long term performance.