Silica needle mat / fabric — properties, λ(T) and computed performance

Service limit ≈1000 °C · density 130–180 kg/m³ · amorphous silica (≥94% SiO2) textiles per supplier datasheets. Supplied as: needle mat and woven fabric — high-temperature removable covers, turbine and exhaust lagging.

Honest assessment

Strengths, limits, verdict

Strengths: 950–1000 °C continuous; flexible; the step past E-glass without going to RCF carcinogen-class handling.

Limits: 2–4x E-glass price; abrasion needs facing fabric.

Verdict: The 550–1000 °C removable-cover core — turbines, exhausts, high-pressure steam.

Thermal conductivity (typical published values)

Mean temperature	λ W/m·K
200 °C	0.055
400 °C	0.080
600 °C	0.110

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

Computed performance · ASTM C680 simplified

Silica needle mat / fabric on real pipe sizes

At 100 °C (λ=0.055 at mean)

Pipe	Thickness	Bare W/m	Insulated W/m	Surface	Saving €/m·yr	t CO2/m·yr
DN50	30 mm	152	35	29 °C	€57	0.21
DN50	50 mm	152	26	25 °C	€61	0.22
DN50	100 mm	152	18	22 °C	€65	0.24
DN100	30 mm	287	57	30 °C	€112	0.41
DN100	50 mm	287	41	26 °C	€120	0.44
DN100	100 mm	287	26	23 °C	€127	0.47
DN200	30 mm	551	98	31 °C	€221	0.81
DN200	50 mm	551	67	27 °C	€236	0.86
DN200	100 mm	551	41	23 °C	€249	0.91

At 250 °C (λ=0.055 at mean)

Pipe	Thickness	Bare W/m	Insulated W/m	Surface	Saving €/m·yr	t CO2/m·yr
DN50	30 mm	436	102	47 °C	€163	0.60
DN50	50 mm	436	76	35 °C	€175	0.64
DN50	100 mm	436	53	26 °C	€187	0.68
DN100	30 mm	826	164	50 °C	€323	1.18
DN100	50 mm	826	117	37 °C	€346	1.27
DN100	100 mm	826	76	28 °C	€366	1.34
DN200	30 mm	1,583	282	52 °C	€635	2.32
DN200	50 mm	1,583	194	39 °C	€678	2.48
DN200	100 mm	1,583	118	29 °C	€715	2.62

At 400 °C (λ=0.056 at mean)

Pipe	Thickness	Bare W/m	Insulated W/m	Surface	Saving €/m·yr	t CO2/m·yr
DN50	30 mm	720	171	65 °C	€268	0.98
DN50	50 mm	720	128	45 °C	€289	1.06
DN50	100 mm	720	89	31 °C	€308	1.13
DN100	30 mm	1,365	276	70 °C	€531	1.94
DN100	50 mm	1,365	197	49 °C	€569	2.08
DN100	100 mm	1,365	128	33 °C	€603	2.21
DN200	30 mm	2,616	476	74 °C	€1,044	3.82
DN200	50 mm	2,616	327	53 °C	€1,117	4.09
DN200	100 mm	2,616	199	35 °C	€1,179	4.31

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 silica needle mat / fabric?

Typical published values: 0.055 W/m·K at 200 °C, 0.080 W/m·K at 400 °C, 0.110 W/m·K at 600 °C (mean temperature). λ rises with temperature — design with the mean-temperature value, not the ambient one.

What is the maximum temperature for silica needle mat / fabric?

≈1000 °C continuous service for typical grades (amorphous silica (≥94% SiO2) textiles per supplier datasheets). Product-specific limits vary — check the datasheet of the exact grade.

Where is silica needle mat / fabric the right choice?

The 550–1000 °C removable-cover core — turbines, exhausts, high-pressure steam.