Insulation·timber 120mm
timber · 120mm
R 0.92
U 0.915 W/m²·K

timber, 120 mm — R 0.92

120 mm divided by a conductivity of 0.13 gives an R-value of 0.92. The U-value is 0.915, so a square metre leaks 18.3 W across a 20-degree difference.

Standards it meets

Not up to any of them yet

Material
timber
Thickness
120 mm
Thermal conductivity
0.13 W/m·K
Thermal resistance
0.92 m²·K/W
U-value
0.915 W/m²·K
Heat lost per square metre
18.3 W
As concrete
1.48 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 panel6 mm
  • phenolic foam18 mm
  • rigid polyurethane21 mm
  • extruded polystyrene26 mm
  • graphite EPS29 mm
  • white EPS33 mm
  • glass wool34 mm
  • mineral wool37 mm
  • cellulose39 mm
  • plasterboard166 mm
  • concrete1477 mm

Nearby cells

timber 100mm
R 0.77
timber 150mm
R 1.15
cellulose 120mm
R 2.86
plasterboard 120mm
R 0.67

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 120mm
R 17.14
phenolic foam 120mm
R 6
rigid polyurethane 120mm
R 5.22
extruded polystyrene 120mm
R 4.29
graphite EPS 120mm
R 3.87
white EPS 120mm
R 3.33
glass wool 120mm
R 3.24
mineral wool 120mm
R 3
cellulose 120mm
R 2.86
timber 120mm
R 0.92
plasterboard 120mm
R 0.67
concrete 120mm
R 0.08

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 120 mm of timber?

0.92 — 120 mm in metres divided by a conductivity of 0.13.

Q. And the U-value?

0.915. That is 1.09 — the resistance plus 0.17 of surface — turned upside down, and a square metre leaks 18.3 W across 20 degrees.

Q. How much concrete would match it?

1.48 metres.

Q. Which standards does it meet?

At 0.915 it does not clear any of them yet.