phenolic foam · 50mm
R 2.5
U 0.375 W/m²·K
phenolic foam, 50 mm — R 2.5
50 mm divided by a conductivity of 0.02 gives an R-value of 2.5. The U-value is 0.375, so a square metre leaks 7.49 W across a 20-degree difference.
Standards it meets
Not up to any of them yet
- Material
- phenolic foam
- Thickness
- 50 mm
- Thermal conductivity
- 0.02 W/m·K
- Thermal resistance
- 2.5 m²·K/W
- U-value
- 0.375 W/m²·K
- Heat lost per square metre
- 7.49 W
- As concrete
- 4 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 panel18 mm
- rigid polyurethane57 mm
- extruded polystyrene70 mm
- graphite EPS78 mm
- white EPS90 mm
- glass wool93 mm
- mineral wool100 mm
- cellulose105 mm
- timber325 mm
- plasterboard450 mm
- concrete4000 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 50 mm of phenolic foam?
2.5 — 50 mm in metres divided by a conductivity of 0.02.
Q. And the U-value?
0.375. That is 2.67 — the resistance plus 0.17 of surface — turned upside down, and a square metre leaks 7.49 W across 20 degrees.
Q. How much concrete would match it?
4 metres.
Q. Which standards does it meet?
At 0.375 it does not clear any of them yet.