Insulation·extruded polystyrene 400mm
extruded polystyrene · 400mm
R 14.29
U 0.069 W/m²·K

extruded polystyrene, 400 mm — R 14.29

400 mm divided by a conductivity of 0.028 gives an R-value of 14.29. The U-value is 0.069, so a square metre leaks 1.38 W across a 20-degree difference.

Standards it meets

  • passive house 0.15
  • Korean central-region wall 0.17
  • loose standard 0.30
Material
extruded polystyrene
Thickness
400 mm
Thermal conductivity
0.028 W/m·K
Thermal resistance
14.29 m²·K/W
U-value
0.069 W/m²·K
Heat lost per square metre
1.38 W
As concrete
22.86 m

Thickness for the same performance

This is the number that shows what insulation is worth. Matching 100 mm of XPS with concrete alone would take 5.7 metres of it. No one builds a wall like that — which is why a concrete building only gets warm once a thin layer of insulation is added.

  • vacuum panel100 mm
  • phenolic foam286 mm
  • rigid polyurethane329 mm
  • graphite EPS443 mm
  • white EPS514 mm
  • glass wool529 mm
  • mineral wool571 mm
  • cellulose600 mm
  • timber1857 mm
  • plasterboard2571 mm
  • concrete22857 mm

Nearby cells

extruded polystyrene 300mm
R 10.71
rigid polyurethane 400mm
R 17.39
graphite EPS 400mm
R 12.9

Same material, other thicknesses

extruded polystyrene 10mm
R 0.36
extruded polystyrene 20mm
R 0.71
extruded polystyrene 30mm
R 1.07
extruded polystyrene 50mm
R 1.79
extruded polystyrene 70mm
R 2.5
extruded polystyrene 100mm
R 3.57
extruded polystyrene 120mm
R 4.29
extruded polystyrene 150mm
R 5.36
extruded polystyrene 200mm
R 7.14
extruded polystyrene 250mm
R 8.93
extruded polystyrene 300mm
R 10.71
extruded polystyrene 400mm
R 14.29

Same thickness, other materials

vacuum panel 400mm
R 57.14
phenolic foam 400mm
R 20
rigid polyurethane 400mm
R 17.39
extruded polystyrene 400mm
R 14.29
graphite EPS 400mm
R 12.9
white EPS 400mm
R 11.11
glass wool 400mm
R 10.81
mineral wool 400mm
R 10
cellulose 400mm
R 9.52
timber 400mm
R 3.08
plasterboard 400mm
R 2.22
concrete 400mm
R 0.25

How to read this

  • Thermal resistance is the thickness in metres divided by the conductivity. Bigger is better.
  • The U-value adds 0.17 of surface resistance and then flips the total. Smaller is better.
  • Resistances add across layers, so a whole wall is the sum of its parts.
  • Conductivity varies by product; the values here are typical for the material.

Frequently asked questions

Q. What is the R-value of 400 mm of extruded polystyrene?

14.29 — 400 mm in metres divided by a conductivity of 0.028.

Q. And the U-value?

0.069. That is 14.46 — the resistance plus 0.17 of surface — turned upside down, and a square metre leaks 1.38 W across 20 degrees.

Q. How much concrete would match it?

22.86 metres.

Q. Which standards does it meet?

At 0.069 it clears 3 of them.