glass wool · 400mm
R 10.81
U 0.091 W/m²·K
glass wool, 400 mm — R 10.81
400 mm divided by a conductivity of 0.037 gives an R-value of 10.81. The U-value is 0.091, so a square metre leaks 1.82 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
- 400 mm
- Thermal conductivity
- 0.037 W/m·K
- Thermal resistance
- 10.81 m²·K/W
- U-value
- 0.091 W/m²·K
- Heat lost per square metre
- 1.82 W
- As concrete
- 17.3 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 panel76 mm
- phenolic foam216 mm
- rigid polyurethane249 mm
- extruded polystyrene303 mm
- graphite EPS335 mm
- white EPS389 mm
- mineral wool432 mm
- cellulose454 mm
- timber1405 mm
- plasterboard1946 mm
- concrete17297 mm
Nearby cells
Same material, other thicknesses
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 400 mm of glass wool?
10.81 — 400 mm in metres divided by a conductivity of 0.037.
Q. And the U-value?
0.091. That is 10.98 — the resistance plus 0.17 of surface — turned upside down, and a square metre leaks 1.82 W across 20 degrees.
Q. How much concrete would match it?
17.3 metres.
Q. Which standards does it meet?
At 0.091 it clears 3 of them.