phenolic foam · 20mm
R 1
U 0.855 W/m²·K
phenolic foam, 20 mm — R 1
20 mm divided by a conductivity of 0.02 gives an R-value of 1. The U-value is 0.855, so a square metre leaks 17.09 W across a 20-degree difference.
Standards it meets
Not up to any of them yet
- Material
- phenolic foam
- Thickness
- 20 mm
- Thermal conductivity
- 0.02 W/m·K
- Thermal resistance
- 1 m²·K/W
- U-value
- 0.855 W/m²·K
- Heat lost per square metre
- 17.09 W
- As concrete
- 1.6 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 panel7 mm
- rigid polyurethane23 mm
- extruded polystyrene28 mm
- graphite EPS31 mm
- white EPS36 mm
- glass wool37 mm
- mineral wool40 mm
- cellulose42 mm
- timber130 mm
- plasterboard180 mm
- concrete1600 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 20 mm of phenolic foam?
1 — 20 mm in metres divided by a conductivity of 0.02.
Q. And the U-value?
0.855. That is 1.17 — the resistance plus 0.17 of surface — turned upside down, and a square metre leaks 17.09 W across 20 degrees.
Q. How much concrete would match it?
1.6 metres.
Q. Which standards does it meet?
At 0.855 it does not clear any of them yet.