Elastomeric foam (FEF) — properties, λ(T) and computed performance

Service limit ≈150 °C · density 40–80 kg/m³ · EN 14304 · ASTM C534. Supplied as: flexible tubes and sheets (Armaflex-type).

Honest assessment

Strengths, limits, verdict

Strengths: built-in vapour barrier (closed cell) — condensation control without separate foil; flexible, clean, fast to fit.

Limits: 150 °C ceiling (most grades 105–125 °C); combustible (B/C class typical); UV degradation outdoors unjacketed.

Verdict: Chilled water, refrigeration and below-ambient lines — the condensation-control default, not a hot-side material.

Thermal conductivity (typical published values)

Mean temperature	λ W/m·K
-20 °C	0.034
0 °C	0.036
20 °C	0.038
40 °C	0.040

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

Computed performance · ASTM C680 simplified

Elastomeric foam (FEF) on real pipe sizes

At 100 °C (λ=0.040 at mean)

Pipe	Thickness	Bare W/m	Insulated W/m	Surface	Saving €/m·yr	t CO2/m·yr
DN50	30 mm	152	27	27 °C	€61	0.22
DN50	50 mm	152	20	24 °C	€64	0.24
DN50	100 mm	152	13	22 °C	€67	0.25
DN100	30 mm	287	43	28 °C	€119	0.44
DN100	50 mm	287	30	24 °C	€125	0.46
DN100	100 mm	287	19	22 °C	€131	0.48
DN200	30 mm	551	74	28 °C	€232	0.85
DN200	50 mm	551	50	25 °C	€244	0.89
DN200	100 mm	551	30	22 °C	€254	0.93

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 140 °C

Material	λ W/m·K	Loss W/m	Surface	Saving €/m·yr	t CO2/m·yr
Stone wool (mineral wool)	0.044	49	27 °C	€186	0.7
Glass wool	0.041	47	27 °C	€187	0.7
Ceramic fibre (RCF / AES blanket)	0.060	66	30 °C	€178	0.7
Aerogel blanket	0.024	28	24 °C	€197	0.7
Calcium silicate	0.059	65	30 °C	€178	0.7
Expanded perlite	0.063	69	30 °C	€176	0.6
Cellular glass	0.050	55	28 °C	€183	0.7
Microporous (fumed-silica) panels	0.022	26	24 °C	€198	0.7
Elastomeric foam (FEF)	0.040	45	27 °C	€188	0.7
PIR / PUR rigid foam	0.028	32	25 °C	€194	0.7
E-glass needle mat	0.045	51	28 °C	€186	0.7
Silica needle mat / fabric	0.055	61	29 °C	€180	0.7

DN100 pipe at 140 °C, 50 mm insulation, per metre of pipe; bare loss 431 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 elastomeric foam (fef)?

Typical published values: 0.034 W/m·K at -20 °C, 0.036 W/m·K at 0 °C, 0.038 W/m·K at 20 °C, 0.040 W/m·K at 40 °C (mean temperature). λ rises with temperature — design with the mean-temperature value, not the ambient one.

What is the maximum temperature for elastomeric foam (fef)?

≈150 °C continuous service for typical grades (EN 14304 · ASTM C534). Product-specific limits vary — check the datasheet of the exact grade.

Where is elastomeric foam (fef) the right choice?

Chilled water, refrigeration and below-ambient lines — the condensation-control default, not a hot-side material.