Glass wool at 400 °C — heat-loss table

λ = 0.064 W/m·K at mean temperature ((400+20)/2 = 210 °C, from the published curve). Pipe losses per metre, four thicknesses, savings vs bare.

Pipe	30 mm W/m	50 mm W/m	80 mm W/m	100 mm W/m	BARE W/m	Surface @50 mm	Saving €/m·yr @50 mm	t CO2/m·yr
DN25	132	104	84	77	399	45 °C	€144	0.53
DN50	193	145	114	102	720	49 °C	€280	1.03
DN80	255	187	142	126	1,061	52 °C	€426	1.56
DN100	310	223	167	146	1,365	53 °C	€557	2.04
DN150	426	299	217	188	2,009	55 °C	€834	3.05
DN200	534	369	264	226	2,616	57 °C	€1,096	4.01
DN300	756	513	359	304	3,867	59 °C	€1,636	5.99

Assumptions: 20 °C ambient, still air (h=10 W/m²·K combined), €0.05/kWh fuel, 8000 h/yr, 82% efficiency, 0.183 kg CO2e/kWh (DESNZ 2024). Flat surfaces at this duty: bare 3,800 W/m² → 434 W/m² at 50 mm (≈€1,642/m²·yr saved). Method: ASTM C680 simplified — methodology. Your exact case: free calculator.

Context

All materials at 400 °C

Material	λ W/m·K	Loss W/m	Surface	Saving €/m·yr	t CO2/m·yr
Stone wool (mineral wool)	0.067	230	54 °C	€553	2.0
Glass wool	0.064	223	53 °C	€557	2.0
Ceramic fibre (RCF / AES blanket)	0.061	214	52 °C	€561	2.1
Aerogel blanket	0.033	119	38 °C	€607	2.2
Calcium silicate	0.076	261	59 °C	€538	2.0
Expanded perlite	0.079	270	60 °C	€534	2.0
Cellular glass	0.068	235	55 °C	€551	2.0
Microporous (fumed-silica) panels	0.024	89	33 °C	€622	2.3
E-glass needle mat	0.060	208	51 °C	€564	2.1
Silica needle mat / fabric	0.056	197	49 °C	€569	2.1

DN100 pipe at 400 °C, 50 mm insulation, per metre of pipe; bare loss 1,365 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).

Material datasheet: Glass wool → · temperature class: by temperature →

FAQ

Questions on this topic

How much heat does a pipe at 400 °C lose with glass wool?

With 50 mm at 400 °C (λ=0.064 at mean): DN50 loses 145 W/m, DN100 223 W/m, DN200 369 W/m — vs 1,365 W/m bare for DN100. Full table on this page.

What surface temperature does glass wool give at 400 °C?

≈53 °C with 50 mm on DN100 (20 °C ambient, still air). Personnel-protection targets (≤45–60 °C) may need more thickness — see the 80/100 mm columns.