phenolic foam · 400mm
R 20
U 0.05 W/m²·K
phenolic foam, 400 mm — R 20
400 mm divided by a conductivity of 0.02 gives an R-value of 20. The U-value is 0.05, so a square metre leaks 0.99 W across a 20-degree difference.
Standards it meets
- passive house 0.15
- Korean central-region wall 0.17
- loose standard 0.30
- Material
- phenolic foam
- Thickness
- 400 mm
- Thermal conductivity
- 0.02 W/m·K
- Thermal resistance
- 20 m²·K/W
- U-value
- 0.05 W/m²·K
- Heat lost per square metre
- 0.99 W
- As concrete
- 32 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 panel140 mm
- rigid polyurethane460 mm
- extruded polystyrene560 mm
- graphite EPS620 mm
- white EPS720 mm
- glass wool740 mm
- mineral wool800 mm
- cellulose840 mm
- timber2600 mm
- plasterboard3600 mm
- concrete32000 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 phenolic foam?
20 — 400 mm in metres divided by a conductivity of 0.02.
Q. And the U-value?
0.05. That is 20.17 — the resistance plus 0.17 of surface — turned upside down, and a square metre leaks 0.99 W across 20 degrees.
Q. How much concrete would match it?
32 metres.
Q. Which standards does it meet?
At 0.05 it clears 3 of them.