What our E rating really means — and why it’s only one part of the story.
Sisalwool is rated Class E for fire – and that might raise questions. But fire safety isn’t one-size-fits-all. Let’s break down what the classification system means, what happens in real-life fires, and how natural insulation like ours performs when it matters most.
What Does Class E Actually Tell You?
Euroclass E is the industry standard for residential properties. This comprises a surface flame test where a small flame (about the size of a lighter) is applied to the material, removed, and the test measures whether it continues to burn or self-extinguishes. Sisalwool passes this test. It self-extinguishes, doesn’t drip or melt, and won’t fuel flame spread like many plastic-based alternatives.
Class E means it’s suitable for homes under 11 metres in England and under 18m in Scotland and not suitable for boundary walls or high-rise/shared living (e.g., flats).
No natural insulation will ever achieve fire ratings A - A1 or A1+ as it requires a non-natural material, such as foil, to cover the insulation.
Real-World Fire Safety: What Matters Most
Fire resistance isn’t just about the insulation. It’s about the full wall system. In a real life fire, you will have plasterboard, that is often fire-rated, covering the insulation that would need to have burnt through first before getting to the insulation. While materials such as foil can help avert fire, they are likely to melt and drip and/or give off toxic gasses such as cyanide, while plastics may not catch fire, but they can melt, allowing drops to set other things alight.
Sisalwool doesn’t melt or emit harmful fumes and to be on the extra safe side, we add a fire-retardent in production. In most homes, it’s protected behind fire-rated plasterboard – offering time and safety before any flame reaches the insulation.
We always recommend an installation that matches your build type and follows local fire regulations and we fully understand the need for a less sustainable product when there is a higher risk involved - such as a care home or block of flats.
