Insulation R-Value Calculator
Add up the thermal resistance of every layer in a wall or roof assembly and see how much each material contributes to the total R-value.
Total R-value (m²K/W)
2.93
Desglose
- U-value (W/m²K)
- 0.34
- Layers counted
- 2
- Biggest contributor
- Mineral wool (R-2.5)
Última actualización:
FAQ
How do I calculate R-value?
R = thickness ÷ thermal conductivity (λ). 100 mm of mineral wool at λ = 0.040 gives R = 0.1/0.04 = 2.5 m²K/W. Total assembly R-value is the sum of all layer R-values plus thin surface film resistances.
How are R-value and U-value related?
They are reciprocals: U = 1/R_total. U-value expresses heat flow per degree of temperature difference, so lower is better. A wall with R = 5 has U = 0.20 W/m²K.
What is a good R-value for a wall?
Modern energy codes typically require whole-wall R-values of 3–6 m²K/W (US R-20–R-35). The insulation layer itself usually contributes 70–85% of the total, as this calculator's 'biggest contributor' line shows.
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