Fire safety in insulation is just as critical as thermal or acoustic performance. Fire-rated and non-combustible insulation can slow the spread of fire, protect structural elements, and provide precious escape time in the event of an emergency.
This guide explains how insulation is tested and classified for fire safety, which materials offer the best performance, and where different types are best used.
Why Fire-Resistant Insulation Matters
Buildings must meet strict fire regulations, especially in high-risk zones like external walls of high-rise buildings, shared party walls, or escape routes. Choosing the right fire-resistant insulation can help:
- Contain and slow down fire spread
- Prevent toxic smoke release
- Protect structural integrity
- Ensure compliance with Building Regulations (especially Approved Document B)
Understanding Fire Ratings
Insulation is tested for reaction to fire and resistance to fire. The two main classification systems used in the UK are:
| System | Explanation |
|---|---|
| Euroclass (EN 13501-1) | Rates combustibility and smoke production from A1 (non-combustible) to F (highly combustible). |
| BS 476 | UK standard testing spread of flame and fire resistance over time. |
Tip: A1 and A2-rated materials are considered non-combustible under Euroclass. These are ideal for fire-critical areas.
Best Fire-Resistant Insulation Types
Here’s a comparison of common insulation types and their typical fire ratings:
| Material | Fire Rating | Best Use Cases |
|---|---|---|
| Rockwool (Stone Wool) | Euroclass A1 – Non-combustible | Walls, floors, ceilings, fire barriers |
| Glass Mineral Wool | Euroclass A1 or A2 | Lofts, partition walls, roofs |
| Calcium Silicate Boards | Euroclass A1 | High-risk areas, commercial settings |
| Phenolic Foam (Treated) | Typically B – Limited combustibility | Walls, floors (where allowed) |
Where to Use Fire-Rated Insulation
- High-rise buildings: Use non-combustible materials (A1/A2) on external walls and cavities.
- Shared party walls: Acoustic + fire-rated insulation helps meet dual regulations.
- Loft conversions & extensions: Materials must comply with both Part B (fire) and Part L (energy efficiency).
- Commercial buildings & schools: Fire regulations are stricter – check spec sheets for compliance.
Fire Safety vs. Thermal Efficiency
When choosing insulation, there's often a trade-off between thermal performance and fire safety, and understanding this balance is essential for safe and efficient buildings.
PIR boards offer excellent thermal insulation in thinner layers, making them ideal where space is tight. However, they are combustible and normally require fire barriers or protective layers especially when used in high risk areas (e.g. flats, shared walls and escape routes).
Materials like mineral wool, glass wool, and natural fibres (e.g. sheep’s wool or hemp) offer excellent fire resistance, though they may need to be installed thicker to match PIR’s thermal rating.
| Insulation Type | Fire Resistance | Thermal Performance |
|---|---|---|
| Mineral Wool | ⭐⭐⭐⭐⭐ | ⭐⭐⭐☆☆ |
| Natural Wool (Sheep’s Wool, Hemp) | ⭐⭐⭐☆☆ | ⭐⭐⭐☆☆ |
| PIR Board | ⭐☆☆☆☆ | ⭐⭐⭐⭐⭐ |
Why Would You Need a Fire Barrier?
A fire barrier is a specially designed layer (often a fire-rated board, sheet, or membrane) that slows or stops the spread of fire and smoke. It can be critical in certain building setups.
Here are some common scenarios where fire barriers are essential:
- In Flats or Apartments: To stop fire from spreading between units through floors, ceilings, or party walls.
- In Loft Conversions: When turning a roof space into a room, barriers may be required between insulation and living space.
- Over Combustible Insulation (e.g., PIR or EPS): These materials can burn — a fire barrier may be necessary to meet safety standards.
- In Cavity Walls or Service Voids: Fire can spread unseen through gaps, pipes, or electrical routes. Barriers help contain it.
Summary: Safe and Smart Choices
Choosing fire-resistant insulation is about protecting people, property, and meeting regulations. Always:
- Check the fire rating (Euroclass or BS)
- Use non-combustible materials in sensitive areas
- Follow building control guidance
- Balance fire safety with performance and sustainability
Have a specific application in mind? Get in touch with our team for a tailored recommendation.