Elastomeric foam vs PIR / PUR rigid foam

Below ambient: elastomeric is its own vapour barrier and flexes around fittings; PIR insulates harder per euro on straight runs but lives or dies by joint vapour-sealing discipline.

Specification

Side by side

	Elastomeric foam (FEF)	PIR / PUR rigid foam
Max service	150 °C	140 °C
Density	40–80	30–50
Standards	EN 14304 · ASTM C534	EN 14308 · ASTM C591
Forms	flexible tubes and sheets (Armaflex-type)	pre-formed sections, slabs

Computed equivalence · DN100

Thickness for the SAME heat loss

Duty	λ Elastomeric foam	λ PIR / PUR rigid foam	Elastomeric foam thickness for EQUAL loss to 50 mm of PIR / PUR rigid foam
100 °C	0.040	0.028	84 mm vs 50 mm

Bisection on the cylindrical conduction equation; λ at mean temperature per each material's published curve. Full per-material tables: Elastomeric foam · PIR / PUR rigid foam.

The whole field at this duty

All materials, DN100 at 100 °C

Material	λ W/m·K	Loss W/m	Surface	Saving €/m·yr	t CO2/m·yr
Stone wool (mineral wool)	0.041	31	25 °C	€125	0.5
Glass wool	0.038	29	24 °C	€126	0.5
Ceramic fibre (RCF / AES blanket)	0.060	44	27 °C	€119	0.4
Aerogel blanket	0.023	18	23 °C	€131	0.5
Calcium silicate	0.056	42	26 °C	€120	0.4
Expanded perlite	0.061	45	27 °C	€118	0.4
Cellular glass	0.047	35	25 °C	€123	0.4
Microporous (fumed-silica) panels	0.022	17	23 °C	€132	0.5
Elastomeric foam (FEF)	0.040	30	24 °C	€125	0.5
PIR / PUR rigid foam	0.028	21	23 °C	€130	0.5
E-glass needle mat	0.045	34	25 °C	€124	0.5
Silica needle mat / fabric	0.055	41	26 °C	€120	0.4

DN100 pipe at 100 °C, 50 mm insulation, per metre of pipe; bare loss 287 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

Is elastomeric foam better than pir / pur rigid foam?

Below ambient: elastomeric is its own vapour barrier and flexes around fittings; PIR insulates harder per euro on straight runs but lives or dies by joint vapour-sealing discipline.

How much thinner can elastomeric foam be than pir / pur rigid foam?

At 100 °C duty, 84 mm of elastomeric foam matches 50 mm of pir / pur rigid foam (computed for a DN100 pipe, ASTM C680 simplified). The ratio shifts with temperature because both λ curves rise at different rates.