Insulation·glass wool 250mm
glass wool · 250mm
R 6.76
U 0.144 W/m²·K

glass wool, 250 mm — R 6.76

250 mm divided by a conductivity of 0.037 gives an R-value of 6.76. The U-value is 0.144, so a square metre leaks 2.89 W across a 20-degree difference.

Standards it meets

  • passive house 0.15
  • Korean central-region wall 0.17
  • loose standard 0.30
Material
glass wool
Thickness
250 mm
Thermal conductivity
0.037 W/m·K
Thermal resistance
6.76 m²·K/W
U-value
0.144 W/m²·K
Heat lost per square metre
2.89 W
As concrete
10.81 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 panel47 mm
  • phenolic foam135 mm
  • rigid polyurethane155 mm
  • extruded polystyrene189 mm
  • graphite EPS209 mm
  • white EPS243 mm
  • mineral wool270 mm
  • cellulose284 mm
  • timber878 mm
  • plasterboard1216 mm
  • concrete10811 mm

Nearby cells

glass wool 200mm
R 5.41
glass wool 300mm
R 8.11
white EPS 250mm
R 6.94
mineral wool 250mm
R 6.25

Same material, other thicknesses

glass wool 10mm
R 0.27
glass wool 20mm
R 0.54
glass wool 30mm
R 0.81
glass wool 50mm
R 1.35
glass wool 70mm
R 1.89
glass wool 100mm
R 2.7
glass wool 120mm
R 3.24
glass wool 150mm
R 4.05
glass wool 200mm
R 5.41
glass wool 250mm
R 6.76
glass wool 300mm
R 8.11
glass wool 400mm
R 10.81

Same thickness, other materials

vacuum panel 250mm
R 35.71
phenolic foam 250mm
R 12.5
rigid polyurethane 250mm
R 10.87
extruded polystyrene 250mm
R 8.93
graphite EPS 250mm
R 8.06
white EPS 250mm
R 6.94
glass wool 250mm
R 6.76
mineral wool 250mm
R 6.25
cellulose 250mm
R 5.95
timber 250mm
R 1.92
plasterboard 250mm
R 1.39
concrete 250mm
R 0.16

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 250 mm of glass wool?

6.76 — 250 mm in metres divided by a conductivity of 0.037.

Q. And the U-value?

0.144. That is 6.93 — the resistance plus 0.17 of surface — turned upside down, and a square metre leaks 2.89 W across 20 degrees.

Q. How much concrete would match it?

10.81 metres.

Q. Which standards does it meet?

At 0.144 it clears 3 of them.