When to Choose Non-Combustible Insulation

When to Choose Non-Combustible Insulation

A1/A2 Fire-Rated Mineral Wool Selection Guide

Non-combustible insulation (A1/A2 fire rating) is required in fire-critical areas and high-temperature applications. This guide explains when mineral wool is necessary and when elastomeric insulation is acceptable.

🔥 What is Non-Combustible Insulation?

Non-combustible insulation has an A1 or A2 fire rating under BS EN 13501-1:

  • A1: Completely non-combustible (stone wool, glass wool)
  • A2: Limited combustibility (mineral wool like K-Rock)

Material: Mineral wool (stone wool or rock wool)

Temperature range: -40°C to +250°C

✅ When Non-Combustible is REQUIRED

1. Fire-Critical Plant Rooms

Commercial plant rooms with fire compartmentation requirements.

Why: Building Regulations Part B requires non-combustible materials in fire-critical areas

Use: K-Rock mineral wool with protective cladding

2. Commercial Risers (Multi-Storey Buildings)

Vertical pipe shafts in buildings over 18m (approx. 6 storeys).

Why: Fire safety regulations for high-rise buildings

Use: A1/A2 rated mineral wool

3. Escape Routes & Corridors

Stairwells, corridors, and designated escape routes.

Why: Must not contribute to fire spread in escape routes

Use: Non-combustible mineral wool only

4. High-Temperature Steam (>105°C)

Steam lines, high-temperature heating, industrial processes.

Why: Elastomeric insulation rated to 105°C max (Solar HT: 150°C)

Use: Mineral wool rated to 250°C

5. Fire-Rated Compartments

Areas with fire compartmentation (30/60/90 minute fire rating).

Why: Maintain fire compartmentation integrity

Use: A1/A2 rated insulation

❌ When Elastomeric is ACCEPTABLE

Class O/1 elastomeric insulation (K-FLEX ST/SK) is acceptable for:

1. Domestic Installations

  • Residential hot water and heating
  • Domestic cold water
  • Home heat pumps

2. Low-Rise Commercial (<18m)

  • Small commercial buildings
  • Retail units
  • Offices (non-high-rise)

3. Chilled Water & Refrigeration

  • Where condensation control is priority
  • Non-fire-critical areas
  • Temperature range -50 to +105°C

4. HVAC (Non-Fire-Critical)

  • Standard HVAC heating/cooling
  • Temperature below 105°C
  • Not in fire-critical plant rooms

📊 Decision Matrix

Application Fire Requirement Temperature Material
Domestic hot water Class O/1 60-80°C Elastomeric or PE
Commercial chilled water Class O/1 (if allowed) 6-12°C Elastomeric (ST/SK)
Fire-critical plant room A1/A2 Any Mineral wool (K-Rock)
Commercial risers A1/A2 Any Mineral wool
High-temp steam A1/A2 >105°C Mineral wool
Escape routes A1/A2 Any Mineral wool
HVAC (non-critical) Class O/1 40-105°C Elastomeric

🔧 Mineral Wool Installation Requirements

1. Requires Protective Cladding

Mineral wool is fibrous and needs protection:

  • Aluminium cladding (most common)
  • PVC cladding (indoor)
  • Stainless steel (high-temp or corrosive environments)

2. Vapour Barrier for Cold Pipes

Mineral wool is NOT closed-cell. For chilled water or refrigeration:

  • Apply external vapour barrier (foil-faced or PVC)
  • Seal all joints vapour-tight
  • Protect with cladding

Alternative: Use elastomeric if fire rating allows (built-in vapour barrier)

3. Pre-Formed Sections

Mineral wool comes in rigid sections:

  • Slower installation than elastomeric tubes
  • Requires pre-formed elbows and fittings
  • Higher labour cost

⚖️ Elastomeric vs Mineral Wool

Choose Elastomeric (K-FLEX) if:

  • ✅ Condensation control is critical (chilled water, refrigeration)
  • ✅ Fast, flexible installation needed
  • ✅ Temperature range -50 to +105°C
  • ✅ Fire rating Class O/1 is acceptable
  • ✅ Not in fire-critical areas

Choose Mineral Wool (K-Rock) if:

  • ✅ Non-combustible (A1/A2) rating required
  • ✅ Fire-critical plant rooms or risers
  • ✅ High-temperature steam (>105°C)
  • ✅ Building Regulations specify A1/A2
  • ✅ Escape routes or fire compartments

📝 Compliance & Documentation

What You Need:

  • Fire test certificates (BS EN 13501-1)
  • Product data sheets (fire rating, thermal performance)
  • Installation records
  • Building Control approval

🛒 Shop Non-Combustible Insulation

📚 Related Guides

Need fire rating advice? Contact our technical team for compliance guidance.