Both are 'ceramic fibre' colloquially. RCF (refractory ceramic fibre, alumino-silicate) serves to ~1200 °C but is classified carcinogen category 1B in the EU — engineering controls, exposure monitoring and substitution pressure apply. AES (alkaline-earth silicate) wools are low-biopersistence (exonerated under EU Note Q), serve to ~1100 °C in current grades, and are the default substitution. Practice: specify AES unless the duty genuinely exceeds it; above that, manage RCF formally or move to engineered solutions (microporous, multi-layer).
Compute your own case: free heat-loss calculator · materials library: 12 datasheets · related: R-value vs k-value (λ) — what's the difference?
