When Non-Combustible Insulation is Required
Not all locations require non-combustible insulation, but getting this wrong in a fire-critical area is a serious compliance failure. The key locations where A1/A2 rated insulation is required are:
- Commercial plant rooms — A1/A2 rated insulation required
- Commercial risers — vertical pipe shafts in multi-storey buildings
- Escape routes — corridors, stairwells, and designated escape routes
- High-rise buildings — buildings over 18m (approx. 6 storeys): non-combustible in risers and plant rooms
- Fire-rated compartments — any area with fire compartmentation requirements
Fire Rating Classifications
| Rating | Classification | Typical Materials |
|---|---|---|
| A1 | Non-combustible | Stone wool, glass wool |
| A2 | Limited combustibility | K-Rock mineral wool |
| Class O/1 | Low flame spread | K-FLEX ST/SK elastomeric |
| C–F | Combustible | Standard foams, untreated plastics — not suitable |
Material Selection by Location
| Location | Required Rating | Recommended Material |
|---|---|---|
| Domestic heating/hot water | Class O/1 | K-FLEX ST/SK or PE |
| Low-rise commercial (under 18m) | Class O/1 | K-FLEX ST/SK |
| Commercial chilled water (non-fire-critical) | Class O/1 | K-FLEX ST/SK |
| Plant rooms (fire-critical) | A1/A2 | K-Rock mineral wool |
| Commercial risers | A1/A2 | K-Rock mineral wool |
| Escape routes | A1/A2 | K-Rock mineral wool |
| High-temp steam (>105°C) | A1/A2 | K-Rock mineral wool |
Fire Stopping at Penetrations
Where pipes pass through fire-rated walls or floors, the insulation alone is not sufficient. You must also use fire-rated collars or wraps to maintain compartmentation, seal gaps with fire-rated sealant, and use non-combustible insulation in the penetration zone. Failure to fire-stop penetrations correctly is one of the most common compliance failures on commercial projects.
Documentation Required
- Fire test certificates to BS EN 13501-1 for all insulation materials used in fire-critical areas
- Product data sheets showing fire rating classification
- Installation records and photographs before any cladding or ceiling closure
- Building Control approval where required
Relevant regulations: Building Regulations Part B (fire safety), Approved Document B, BS 9999.
Common Mistakes
- Using Class O/1 elastomeric in fire-critical plant rooms where A1/A2 is required
- Not checking fire rating requirements before specifying insulation
- Leaving mineral wool unprotected — it requires cladding in most applications
- Not fire-stopping pipe penetrations through compartment walls and floors
- Missing fire test certificates at handover
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