Insulation·timber 20mm
timber · 20mm
R 0.15
U 3.088 W/m²·K

timber, 20 mm — R 0.15

20 mm divided by a conductivity of 0.13 gives an R-value of 0.15. The U-value is 3.088, so a square metre leaks 61.76 W across a 20-degree difference.

Standards it meets

Not up to any of them yet

Material
timber
Thickness
20 mm
Thermal conductivity
0.13 W/m·K
Thermal resistance
0.15 m²·K/W
U-value
3.088 W/m²·K
Heat lost per square metre
61.76 W
As concrete
0.25 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 panel1 mm
  • phenolic foam3 mm
  • rigid polyurethane4 mm
  • extruded polystyrene4 mm
  • graphite EPS5 mm
  • white EPS6 mm
  • glass wool6 mm
  • mineral wool6 mm
  • cellulose6 mm
  • plasterboard28 mm
  • concrete246 mm

Nearby cells

timber 10mm
R 0.08
timber 30mm
R 0.23
cellulose 20mm
R 0.48
plasterboard 20mm
R 0.11

Same material, other thicknesses

timber 10mm
R 0.08
timber 20mm
R 0.15
timber 30mm
R 0.23
timber 50mm
R 0.38
timber 70mm
R 0.54
timber 100mm
R 0.77
timber 120mm
R 0.92
timber 150mm
R 1.15
timber 200mm
R 1.54
timber 250mm
R 1.92
timber 300mm
R 2.31
timber 400mm
R 3.08

Same thickness, other materials

vacuum panel 20mm
R 2.86
phenolic foam 20mm
R 1
rigid polyurethane 20mm
R 0.87
extruded polystyrene 20mm
R 0.71
graphite EPS 20mm
R 0.65
white EPS 20mm
R 0.56
glass wool 20mm
R 0.54
mineral wool 20mm
R 0.5
cellulose 20mm
R 0.48
timber 20mm
R 0.15
plasterboard 20mm
R 0.11
concrete 20mm
R 0.01

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 timber?

0.15 — 20 mm in metres divided by a conductivity of 0.13.

Q. And the U-value?

3.088. That is 0.32 — the resistance plus 0.17 of surface — turned upside down, and a square metre leaks 61.76 W across 20 degrees.

Q. How much concrete would match it?

0.25 metres.

Q. Which standards does it meet?

At 3.088 it does not clear any of them yet.