Insulation for 250–400 °C — HP steam, hot-oil heaters, exhaust lines

Per the Inzonex temperature tiers: wired mat 100 mm territory. Surface-temperature compliance (≤45–60 °C) starts driving thickness as much as economics; bare-component losses get brutal — a bare DN150 valve at 350 °C wastes more than a small house uses.

Valid materials

What survives 250–400 °C

Material (serves this class)	Max service	λ at 325 °C duty
Stone wool (mineral wool)	640 °C	0.059
Glass wool	450 °C	0.056
Ceramic fibre (RCF / AES blanket)	1200 °C	0.060
Aerogel blanket	650 °C	0.030
Calcium silicate	650 °C	0.071
Expanded perlite	650 °C	0.074
Cellular glass	430 °C	0.064
Microporous (fumed-silica) panels	1000 °C	0.023
E-glass needle mat	550 °C	0.054
Silica needle mat / fabric	1000 °C	0.055

Computed · DN100 at 325 °C, 50 mm

The numbers at this temperature

Material	λ W/m·K	Loss W/m	Surface	Saving €/m·yr	t CO2/m·yr
Stone wool (mineral wool)	0.059	166	45 °C	€454	1.7
Glass wool	0.056	159	44 °C	€457	1.7
Ceramic fibre (RCF / AES blanket)	0.060	168	45 °C	€452	1.7
Aerogel blanket	0.030	88	33 °C	€491	1.8
Calcium silicate	0.071	197	49 °C	€438	1.6
Expanded perlite	0.074	204	50 °C	€435	1.6
Cellular glass	0.064	177	46 °C	€448	1.6
Microporous (fumed-silica) panels	0.023	69	30 °C	€501	1.8
E-glass needle mat	0.054	154	43 °C	€459	1.7
Silica needle mat / fabric	0.055	155	43 °C	€459	1.7

DN100 pipe at 325 °C, 50 mm insulation, per metre of pipe; bare loss 1,095 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).

FAQ

Questions on this topic

What insulation is best for 250–400 °c?

Shortlist for HP steam, hot-oil heaters, exhaust lines: Stone wool (mineral wool), E-glass needle mat, Calcium silicate, Aerogel blanket. Per the Inzonex temperature tiers: wired mat 100 mm territory.

How much heat does a pipe at 325 °C lose?

A bare DN100 pipe at 325 °C loses ≈1,095 W per metre in still air (ASTM C680 simplified). 50 mm of stone wool (mineral wool) cuts that to ≈166 W/m — ≈€454 and 1.66 t CO2 saved per metre·year at €0.05/kWh.