Stone wool (rock wool / mineral wool) — properties, λ(T) and computed performance

Also marketed as rock wool (basalt-based; the terms are explained here). Service limit ≈640 °C · density 80–150 kg/m³ · EN 14303 · ASTM C547 (pipe) / C592 (wired mat) / C612 (board). Supplied as: wired mats, pipe sections, slabs, loose wool; the workhorse core of removable covers up to ~600 °C.

Honest assessment

Strengths, limits, verdict

Strengths: best cost-per-performance 100–600 °C; non-combustible (A1); melt point >1000 °C; widely available in every format.

Limits: loses performance wet (CUI risk if jacket leaks); dust during fitting; sags in vibration unless stitched/wired.

Verdict: The default industrial choice from steam to 600 °C — every alternative must justify its premium against stone wool.

Thermal conductivity (typical published values)

Mean temperature	λ W/m·K
10 °C	0.036
50 °C	0.040
100 °C	0.046
200 °C	0.064
300 °C	0.089
400 °C	0.121

λ at mean temperature — rises with T because pore radiation grows with T³.

Computed performance · ASTM C680 simplified

Stone wool (mineral wool) on real pipe sizes

At 100 °C (λ=0.041 at mean)

Pipe	Thickness	Bare W/m	Insulated W/m	Surface	Saving €/m·yr	t CO2/m·yr
DN50	30 mm	152	27	27 °C	€61	0.22
DN50	50 mm	152	20	24 °C	€64	0.23
DN50	100 mm	152	14	22 °C	€67	0.25
DN100	30 mm	287	44	28 °C	€119	0.43
DN100	50 mm	287	31	25 °C	€125	0.46
DN100	100 mm	287	20	22 °C	€130	0.48
DN200	30 mm	551	76	29 °C	€231	0.85
DN200	50 mm	551	52	25 °C	€243	0.89
DN200	100 mm	551	31	22 °C	€253	0.93

At 250 °C (λ=0.052 at mean)

Pipe	Thickness	Bare W/m	Insulated W/m	Surface	Saving €/m·yr	t CO2/m·yr
DN50	30 mm	436	97	46 °C	€165	0.60
DN50	50 mm	436	72	34 °C	€177	0.65
DN50	100 mm	436	50	26 °C	€188	0.69
DN100	30 mm	826	157	49 °C	€326	1.19
DN100	50 mm	826	112	37 °C	€348	1.28
DN100	100 mm	826	72	27 °C	€368	1.35
DN200	30 mm	1,583	270	51 °C	€640	2.34
DN200	50 mm	1,583	185	38 °C	€682	2.50
DN200	100 mm	1,583	112	29 °C	€718	2.63

At 400 °C (λ=0.067 at mean)

Pipe	Thickness	Bare W/m	Insulated W/m	Surface	Saving €/m·yr	t CO2/m·yr
DN50	30 mm	720	198	72 °C	€254	0.93
DN50	50 mm	720	150	50 °C	€278	1.02
DN50	100 mm	720	105	33 °C	€300	1.10
DN100	30 mm	1,365	319	78 °C	€510	1.87
DN100	50 mm	1,365	230	54 °C	€553	2.03
DN100	100 mm	1,365	151	35 °C	€592	2.17
DN200	30 mm	2,616	548	83 °C	€1,009	3.69
DN200	50 mm	2,616	380	58 °C	€1,090	3.99
DN200	100 mm	2,616	233	38 °C	€1,162	4.25

Assumptions: 20 °C ambient, still air (h=10 W/m²·K), €0.05/kWh fuel, 8000 h/yr, 82% boiler efficiency, 0.183 kg CO2e/kWh. Your numbers: free calculator.

Against the field

Same duty, all materials — DN100 at 250 °C

Material	λ W/m·K	Loss W/m	Surface	Saving €/m·yr	t CO2/m·yr
Stone wool (mineral wool)	0.052	112	37 °C	€348	1.3
Glass wool	0.050	106	36 °C	€351	1.3
Ceramic fibre (RCF / AES blanket)	0.060	127	39 °C	€341	1.2
Aerogel blanket	0.027	61	29 °C	€373	1.4
Calcium silicate	0.067	139	41 °C	€335	1.2
Expanded perlite	0.070	145	42 °C	€332	1.2
Cellular glass	0.058	122	38 °C	€343	1.3
Microporous (fumed-silica) panels	0.023	50	27 °C	€378	1.4
E-glass needle mat	0.050	106	36 °C	€351	1.3
Silica needle mat / fabric	0.055	117	37 °C	€346	1.3

DN100 pipe at 250 °C, 50 mm insulation, per metre of pipe; bare loss 826 W/m. λ at mean temperature; € and CO2 per metre·year at €0.05/kWh, 8000 h, 82% efficiency. Method: ASTM C680 simplified (h=10).

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FAQ

Questions on this topic

What is the thermal conductivity of stone wool (mineral wool)?

Typical published values: 0.036 W/m·K at 10 °C, 0.040 W/m·K at 50 °C, 0.046 W/m·K at 100 °C, 0.064 W/m·K at 200 °C, 0.089 W/m·K at 300 °C, 0.121 W/m·K at 400 °C (mean temperature). λ rises with temperature — design with the mean-temperature value, not the ambient one.

What is the maximum temperature for stone wool (mineral wool)?

≈640 °C continuous service for typical grades (EN 14303 · ASTM C547 (pipe) / C592 (wired mat) / C612 (board)). Product-specific limits vary — check the datasheet of the exact grade.

Where is stone wool (mineral wool) the right choice?

The default industrial choice from steam to 600 °C — every alternative must justify its premium against stone wool.