A Practical Comparison
Both materials insulate pipe effectively, but they suit different applications. The choice comes down to operating temperature, condensation risk, fire requirements, and installation environment.
| Feature | Elastomeric (K-FLEX ST/SK) | Mineral Wool (K-Rock) |
|---|---|---|
| Temperature range | -50°C to +105°C (Solar HT: +150°C) | -40°C to +250°C |
| Moisture resistance | Excellent — closed-cell, built-in vapour barrier | Requires a separate vapour barrier |
| Fire rating | Class O / Class 1 | Non-combustible (A1/A2) |
| Installation | Fast, flexible, self-seal SK option | Rigid sections require cladding |
| Best for | Chilled water, refrigeration, HVAC | High-temp steam, fire-critical areas |
| Total installed cost | Mid-range | Higher (material + cladding + labour) |
When to Choose Elastomeric
K-FLEX ST/SK elastomeric is the standard choice for the majority of HVAC and refrigeration work: chilled water (6–12°C), refrigeration lines (-30 to +10°C), heat pump pipework, HVAC heating and cooling up to 105°C, and domestic hot and cold water.
Key advantages: The closed-cell structure acts as its own vapour barrier — no additional wrapping needed. The SK self-seal range speeds up installation significantly. Flexible tubes fit around bends and complex pipework without pre-formed sections. No cladding required for most indoor applications.
Limitations: Not suitable above 105°C (except Solar HT grade). Not non-combustible — don't specify it for fire-critical areas where A1/A2 is required.
When to Choose Mineral Wool
K-Rock mineral wool is the right choice when temperature exceeds 105°C or when Building Regulations require non-combustible insulation: high-temperature steam lines, fire-critical plant rooms, commercial risers, and industrial heating systems.
Key advantages: Non-combustible A1/A2 fire rating. Handles up to 250°C. Required by regulation in plant rooms, commercial risers, and escape routes.
Limitations: Requires a separate vapour barrier on cold applications. Rigid sections are slower to install. Needs protective cladding in most applications, adding cost and labour time.
Quick Decision Guide
Choose elastomeric if: chilled water, refrigeration, or standard HVAC; condensation control is critical; temperature below 105°C; Class O/1 fire rating is acceptable.
Choose mineral wool if: temperature exceeds 105°C; non-combustible insulation is required by specification or regulation; working in fire-critical plant rooms or commercial risers.
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