Insulation·extruded polystyrene 70mm
extruded polystyrene · 70mm
R 2.5
U 0.375 W/m²·K

extruded polystyrene, 70 mm — R 2.5

70 mm divided by a conductivity of 0.028 gives an R-value of 2.5. The U-value is 0.375, so a square metre leaks 7.49 W across a 20-degree difference.

Standards it meets

Not up to any of them yet

Material
extruded polystyrene
Thickness
70 mm
Thermal conductivity
0.028 W/m·K
Thermal resistance
2.5 m²·K/W
U-value
0.375 W/m²·K
Heat lost per square metre
7.49 W
As concrete
4 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 panel18 mm
  • phenolic foam50 mm
  • rigid polyurethane57 mm
  • graphite EPS78 mm
  • white EPS90 mm
  • glass wool93 mm
  • mineral wool100 mm
  • cellulose105 mm
  • timber325 mm
  • plasterboard450 mm
  • concrete4000 mm

Nearby cells

extruded polystyrene 50mm
R 1.79
extruded polystyrene 100mm
R 3.57
rigid polyurethane 70mm
R 3.04
graphite EPS 70mm
R 2.26

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 70mm
R 10
phenolic foam 70mm
R 3.5
rigid polyurethane 70mm
R 3.04
extruded polystyrene 70mm
R 2.5
graphite EPS 70mm
R 2.26
white EPS 70mm
R 1.94
glass wool 70mm
R 1.89
mineral wool 70mm
R 1.75
cellulose 70mm
R 1.67
timber 70mm
R 0.54
plasterboard 70mm
R 0.39
concrete 70mm
R 0.04

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 70 mm of extruded polystyrene?

2.5 — 70 mm in metres divided by a conductivity of 0.028.

Q. And the U-value?

0.375. That is 2.67 — the resistance plus 0.17 of surface — turned upside down, and a square metre leaks 7.49 W across 20 degrees.

Q. How much concrete would match it?

4 metres.

Q. Which standards does it meet?

At 0.375 it does not clear any of them yet.