U-Value and Insulation Calculator
Thermal transmittance and resistance of an insulation layer, from thickness and conductivity.
Results
U-value
0.3303
W/(m²·K)
Thermal resistance R
3.0271
m²·K/W
Thermal resistance R
2.8571
m²·K/W
What this tool does
The lower the U-value, the less heat escapes. Typical conductivities are 0.035 W/(m·K) for mineral wool, 0.038 for EPS and 0.022 for polyurethane; the surface resistance of 0.17 is the usual combined value for a wall.
Formula
R = Rsi + e ÷ λ + Rse · U = 1 ÷ R
Variables
| Symbol | Meaning | Unit |
|---|---|---|
es | Thickness | cm |
k | Thermal conductivity λ | W/(m·K) |
rs | Thermal resistance R | m²·K/W |
U | U-value | W/(m²·K) |
R | Thermal resistance R | m²·K/W |
RM | Thermal resistance R | m²·K/W |
Worked example
- Thickness10 cm
- Thermal conductivity λ0.035 W/(m·K)
- Thermal resistance R0.17 m²·K/W
- U-value0.3303 W/(m²·K)
- Thermal resistance R3.0271 m²·K/W
- Thermal resistance R2.8571 m²·K/W
Limitations
- For work that must comply with a standard or be signed off, check the result against the applicable code and have it reviewed by a qualified engineer.
- The result is an estimate based only on the values you type. Real situations often include factors this calculator does not know about.