Mineral Wool vs Ceramic Fibre: Cost, Temperature, and Where Each Belongs
Ceramic fibre reaches 1260°C; mineral wool costs a fraction as much per square metre. How to decide which belongs where across a plant, and why using fibre everywhere wastes budget.
This comparison usually gets framed as a performance question when it is mostly an economics question. Ceramic fibre outperforms mineral wool on temperature and thermal mass by a wide margin. It also costs considerably more per square metre — and most of the insulated surface area in a typical plant does not need what it offers.
The short answer
Use ceramic fibre where temperature or thermal mass demands it. Use mineral wool everywhere else. Specifying fibre across general plant insulation wastes budget that would deliver more if spent closing gaps elsewhere.
Side-by-side comparison
| Property | Ceramic fibre | Mineral wool / rockwool |
|---|---|---|
| Continuous service temperature | Up to 1260°C | 600°C (blanket) to 1000°C (board) |
| Thermal mass | Very low | Moderate |
| Relative cost per m² | High | Low |
| Behaviour when wet | Loses performance | Loses performance permanently |
| Load-bearing | No | No — compresses |
| Acoustic attenuation | Limited | Good |
| Typical role | Furnace and kiln hot face | Ducting, casings, pipework, vessels |
Where ceramic fibre is required
Two cases justify the cost difference clearly.
Temperature above mineral wool's range. Furnace and kiln hot faces, reheat furnace roofs, and boiler walls operating above 1000°C are simply outside what rockwool can do. Ceramic fibre is the only one of the two that survives.
Equipment that cycles frequently. On batch kilns, shuttle kilns, and furnaces that start and stop, thermal mass drives fuel consumption. Fibre stores very little heat, so a much larger share of the fuel reaches the product instead of the lining. This argument does not apply to continuously fired equipment.
Where mineral wool is the better choice
Most of a plant, by surface area. Flue ducts, economiser casings, vessel walls, storage tanks, condensate lines, and long runs of process pipework all operate well below 1000°C and carry no requirement that fibre uniquely satisfies.
Across those areas rockwool delivers good thermal performance, non-combustibility, and useful acoustic attenuation at a fraction of the cost. Given that insulation budgets are finite, spending them on fibre where wool would do usually means leaving other areas uninsulated — which is a net loss.
Grades within the mineral wool family
One practical caution: the range inside the family is wide and the grades are not interchangeable.
- Rockwool insulation board (1000°C) — duct casings, vessel walls, equipment enclosures.
- Rockwool insulation blanket (600°C) — wrapping curved and irregular surfaces.
- Thermal insulation roll — long continuous pipe runs, minimising joints.
Specifying the 600°C blanket on a surface running at 800°C will degrade it quickly, and this is a common error precisely because both products are described as rockwool.
What neither material solves
Both compress under load, so neither belongs at a pipe support — that requires rigid calcium silicate. And both lose most of their performance when wet, without fully recovering on drying.
In outdoor and humid installations the vapour barrier and cladding detail matter more than the choice between these two materials. An expensive fibre installation with unsealed cladding laps will underperform a cheap rockwool installation that stays dry.
Material cost versus installed cost
Comparing these two on price per square metre understates the picture, because installation labour, cladding, fixings, and anchoring often exceed the insulation cost itself. Two consequences follow.
First, on a large ducting or casing job the labour is broadly similar whichever material is fitted, so the premium for fibre is diluted — but it is still a premium paid for capability that is not being used. Second, and more importantly, if a material has to be replaced early because it was specified into the wrong service, the replacement cost includes the full labour and cladding again. The cheapest installation is the one that does not have to be redone.
This is why the allocation question matters more than the unit price question. Getting fibre and wool into the right positions saves more than negotiating either price.
Handling and site practice
Both materials are fibrous and both require sensible handling precautions during cutting and installation — ventilation, appropriate personal protective equipment, and following the manufacturer's guidance. Rockwool is generally the easier material to work with on large areas and cuts cleanly with a knife. Ceramic fibre is lighter but more friable, and offcuts tend to be less reusable.
Storage matters for both. Neither should be stored where it can get wet before installation, because wet material installed wet will not dry properly inside a clad system and will underperform from day one.
A practical allocation
For a typical plant: ceramic fibre on furnace and kiln hot faces and on cycling equipment; rockwool across ducting, casings, tanks, and general pipework; calcium silicate at supports and on high-pressure steam; textiles at joints and seals. Each material doing the job it is good at, rather than one material used everywhere.
Worked through on a boiler house, that typically means fibre confined to the combustion chamber surrounds and boiler walls — a small fraction of the total area — with rockwool covering the flue ducts, economiser casings, and the bulk of the pipework, and calcium silicate reserved for the main steam header and support positions. The fibre line item looks small on the order and does the work that only fibre can do.
See also Ceramic Fibre vs Calcium Silicate for the load-bearing side of the decision, and our industrial thermal insulation guide for the full selection framework.