Expanded perlite Insulation — λ(T), Max Temperature, Computed Heat Loss

Honest assessment

Strengths, limits, verdict

Strengths: rigid, non-combustible, low chloride content (austenitic stainless friendly), hydrophobic grades standard.

Limits: similar weight/handling burden to calcium silicate; availability varies by region.

Verdict: The calcium-silicate alternative specified where chloride-induced SCC on stainless is the fear.

Thermal conductivity (typical published values)

Mean temperature	λ W/m·K
50 °C	0.060
100 °C	0.065
200 °C	0.078
300 °C	0.092

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

Computed performance · ASTM C680 simplified

Expanded perlite on real pipe sizes

At 100 °C (λ=0.061 at mean)

Pipe	Thickness	Bare W/m	Insulated W/m	Surface	Saving €/m·yr	t CO2/m·yr
DN50	30 mm	152	39	30 °C	€55	0.20
DN50	50 mm	152	29	26 °C	€60	0.22
DN50	100 mm	152	20	22 °C	€64	0.23
DN100	30 mm	287	62	31 °C	€110	0.40
DN100	50 mm	287	45	27 °C	€118	0.43
DN100	100 mm	287	29	23 °C	€126	0.46
DN200	30 mm	551	107	32 °C	€216	0.79
DN200	50 mm	551	74	27 °C	€233	0.85
DN200	100 mm	551	45	23 °C	€247	0.90

At 250 °C (λ=0.070 at mean)

Pipe	Thickness	Bare W/m	Insulated W/m	Surface	Saving €/m·yr	t CO2/m·yr
DN50	30 mm	436	125	53 °C	€152	0.56
DN50	50 mm	436	94	39 °C	€166	0.61
DN50	100 mm	436	66	28 °C	€180	0.66
DN100	30 mm	826	200	57 °C	€305	1.12
DN100	50 mm	826	145	42 °C	€332	1.22
DN100	100 mm	826	95	30 °C	€356	1.30
DN200	30 mm	1,583	344	59 °C	€604	2.21
DN200	50 mm	1,583	240	44 °C	€655	2.40
DN200	100 mm	1,583	147	31 °C	€700	2.56

At 400 °C (λ=0.079 at mean)

Pipe	Thickness	Bare W/m	Insulated W/m	Surface	Saving €/m·yr	t CO2/m·yr
DN50	30 mm	720	230	81 °C	€239	0.87
DN50	50 mm	720	176	55 °C	€265	0.97
DN50	100 mm	720	124	35 °C	€290	1.06
DN100	30 mm	1,365	370	87 °C	€485	1.78
DN100	50 mm	1,365	270	60 °C	€534	1.95
DN100	100 mm	1,365	179	38 °C	€579	2.12
DN200	30 mm	2,616	634	92 °C	€967	3.54
DN200	50 mm	2,616	445	64 °C	€1,059	3.87
DN200	100 mm	2,616	276	41 °C	€1,141	4.18

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).

Head-to-heads featuring this material: comparison library →

FAQ

Questions on this topic

What is the thermal conductivity of expanded perlite?

Typical published values: 0.060 W/m·K at 50 °C, 0.065 W/m·K at 100 °C, 0.078 W/m·K at 200 °C, 0.092 W/m·K at 300 °C (mean temperature). λ rises with temperature — design with the mean-temperature value, not the ambient one.

What is the maximum temperature for expanded perlite?

≈650 °C continuous service for typical grades (ASTM C610). Product-specific limits vary — check the datasheet of the exact grade.

Where is expanded perlite the right choice?

The calcium-silicate alternative specified where chloride-induced SCC on stainless is the fear.

Expanded perlite — properties, λ(T) and computed performance