Calcium silicate Insulation — λ(T), Max Temperature, Computed Heat Loss

Honest assessment

Strengths, limits, verdict

Strengths: rigid and walkable (load-bearing); survives 650 °C; non-wicking grades exist; the refinery classic.

Limits: heavy; needs cutting to fit; absorbs water if unjacketed (classic CUI substrate); slower to install than flexible.

Verdict: Where mechanical abuse and foot traffic rule — pipe racks, walked lines — rigidity beats lambda.

Thermal conductivity (typical published values)

Mean temperature	λ W/m·K
50 °C	0.055
100 °C	0.062
200 °C	0.075
300 °C	0.089
400 °C	0.104

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

Computed performance · ASTM C680 simplified

Calcium silicate on real pipe sizes

At 100 °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	152	36	30 °C	€56	0.21
DN50	50 mm	152	27	25 °C	€61	0.22
DN50	100 mm	152	19	22 °C	€65	0.24
DN100	30 mm	287	58	31 °C	€112	0.41
DN100	50 mm	287	42	26 °C	€120	0.44
DN100	100 mm	287	27	23 °C	€127	0.46
DN200	30 mm	551	100	31 °C	€220	0.80
DN200	50 mm	551	69	27 °C	€235	0.86
DN200	100 mm	551	42	23 °C	€248	0.91

At 250 °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	436	120	52 °C	€154	0.56
DN50	50 mm	436	91	38 °C	€168	0.62
DN50	100 mm	436	64	28 °C	€182	0.66
DN100	30 mm	826	193	55 °C	€309	1.13
DN100	50 mm	826	139	41 °C	€335	1.23
DN100	100 mm	826	91	29 °C	€358	1.31
DN200	30 mm	1,583	332	58 °C	€610	2.23
DN200	50 mm	1,583	230	43 °C	€660	2.42
DN200	100 mm	1,583	141	31 °C	€703	2.57

At 400 °C (λ=0.076 at mean)

Pipe	Thickness	Bare W/m	Insulated W/m	Surface	Saving €/m·yr	t CO2/m·yr
DN50	30 mm	720	223	79 °C	€242	0.89
DN50	50 mm	720	170	54 °C	€268	0.98
DN50	100 mm	720	120	35 °C	€293	1.07
DN100	30 mm	1,365	358	85 °C	€491	1.80
DN100	50 mm	1,365	261	59 °C	€538	1.97
DN100	100 mm	1,365	172	37 °C	€582	2.13
DN200	30 mm	2,616	615	90 °C	€976	3.57
DN200	50 mm	2,616	430	63 °C	€1,066	3.90
DN200	100 mm	2,616	266	40 °C	€1,146	4.19

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 calcium silicate?

Typical published values: 0.055 W/m·K at 50 °C, 0.062 W/m·K at 100 °C, 0.075 W/m·K at 200 °C, 0.089 W/m·K at 300 °C, 0.104 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 calcium silicate?

≈650 °C continuous service for typical grades (ASTM C533 Type I). Product-specific limits vary — check the datasheet of the exact grade.

Where is calcium silicate the right choice?

Where mechanical abuse and foot traffic rule — pipe racks, walked lines — rigidity beats lambda.

Calcium silicate — properties, λ(T) and computed performance