Material datasheet

Glass wool — properties, λ(T) and computed performance

Service limit ≈450 °C · density 24–80 kg/m³ · EN 14303 · ASTM C547 / C553. Supplied as: pipe sections, rolls, lamella mats — lighter and cheaper than stone wool.

Honest assessment

Strengths, limits, verdict

Strengths: lowest cost below ~250 °C; lighter handling; slightly better lambda than stone wool when cold-side.

Limits: service limit ~400–450 °C; lower compressive strength; same moisture sensitivity.

Verdict: Hot-water and low-pressure-steam economics champion; step up to stone wool past ~250 °C.

Thermal conductivity (typical published values)

Mean temperature	λ W/m·K
10 °C	0.033
50 °C	0.037
100 °C	0.044
150 °C	0.052
200 °C	0.062
250 °C	0.074

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

Computed performance · ASTM C680 simplified

Glass wool on real pipe sizes

At 100 °C (λ=0.038 at mean)

Pipe	Thickness	Bare W/m	Insulated W/m	Surface	Saving €/m·yr	t CO2/m·yr
DN50	30 mm	152	26	27 °C	€61	0.22
DN50	50 mm	152	19	24 °C	€65	0.24
DN50	100 mm	152	13	22 °C	€68	0.25
DN100	30 mm	287	41	28 °C	€120	0.44
DN100	50 mm	287	29	24 °C	€126	0.46
DN100	100 mm	287	19	22 °C	€131	0.48
DN200	30 mm	551	72	28 °C	€234	0.86
DN200	50 mm	551	48	25 °C	€245	0.90
DN200	100 mm	551	29	22 °C	€254	0.93

At 250 °C (λ=0.050 at mean)

Pipe	Thickness	Bare W/m	Insulated W/m	Surface	Saving €/m·yr	t CO2/m·yr
DN50	30 mm	436	93	45 °C	€167	0.61
DN50	50 mm	436	69	34 °C	€179	0.65
DN50	100 mm	436	48	26 °C	€189	0.69
DN100	30 mm	826	150	47 °C	€330	1.21
DN100	50 mm	826	106	36 °C	€351	1.28
DN100	100 mm	826	69	27 °C	€369	1.35
DN200	30 mm	1,583	258	49 °C	€646	2.37
DN200	50 mm	1,583	176	38 °C	€686	2.51
DN200	100 mm	1,583	107	28 °C	€720	2.64

At 400 °C (λ=0.064 at mean)

Pipe	Thickness	Bare W/m	Insulated W/m	Surface	Saving €/m·yr	t CO2/m·yr
DN50	30 mm	720	193	71 °C	€257	0.94
DN50	50 mm	720	145	49 °C	€280	1.03
DN50	100 mm	720	102	32 °C	€302	1.10
DN100	30 mm	1,365	310	77 °C	€514	1.88
DN100	50 mm	1,365	223	53 °C	€557	2.04
DN100	100 mm	1,365	146	35 °C	€594	2.18
DN200	30 mm	2,616	534	81 °C	€1,016	3.72
DN200	50 mm	2,616	369	57 °C	€1,096	4.01
DN200	100 mm	2,616	226	37 °C	€1,166	4.27

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 glass wool?

Typical published values: 0.033 W/m·K at 10 °C, 0.037 W/m·K at 50 °C, 0.044 W/m·K at 100 °C, 0.052 W/m·K at 150 °C, 0.062 W/m·K at 200 °C, 0.074 W/m·K at 250 °C (mean temperature). λ rises with temperature — design with the mean-temperature value, not the ambient one.

What is the maximum temperature for glass wool?

≈450 °C continuous service for typical grades (EN 14303 · ASTM C547 / C553). Product-specific limits vary — check the datasheet of the exact grade.

Where is glass wool the right choice?

Hot-water and low-pressure-steam economics champion; step up to stone wool past ~250 °C.