extruded polystyrene · 20mm
R 0.71
U 1.131 W/m²·K
extruded polystyrene, 20 mm — R 0.71
20 mm divided by a conductivity of 0.028 gives an R-value of 0.71. The U-value is 1.131, so a square metre leaks 22.62 W across a 20-degree difference.
Standards it meets
Not up to any of them yet
- Material
- extruded polystyrene
- Thickness
- 20 mm
- Thermal conductivity
- 0.028 W/m·K
- Thermal resistance
- 0.71 m²·K/W
- U-value
- 1.131 W/m²·K
- Heat lost per square metre
- 22.62 W
- As concrete
- 1.14 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 panel5 mm
- phenolic foam14 mm
- rigid polyurethane16 mm
- graphite EPS22 mm
- white EPS26 mm
- glass wool26 mm
- mineral wool29 mm
- cellulose30 mm
- timber93 mm
- plasterboard129 mm
- concrete1143 mm
Nearby cells
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
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 20 mm of extruded polystyrene?
0.71 — 20 mm in metres divided by a conductivity of 0.028.
Q. And the U-value?
1.131. That is 0.88 — the resistance plus 0.17 of surface — turned upside down, and a square metre leaks 22.62 W across 20 degrees.
Q. How much concrete would match it?
1.14 metres.
Q. Which standards does it meet?
At 1.131 it does not clear any of them yet.