Thermal Resistance Calculator Formula
Understand the math behind the thermal resistance calculator. Each variable explained with a worked example.
Formulas Used
Thermal Resistance
thermal_resistance = thickness / conductivityVariables
| Variable | Description | Default |
|---|---|---|
thickness | Material Thickness(m) | 0.1 |
conductivity | Thermal Conductivity(W/(m·K)) | 0.04 |
How It Works
Thermal Resistance
Thermal resistance quantifies how well a material layer resists heat flow.
Formula
R = d / k
where d is thickness and k is thermal conductivity. Higher R means better insulation. For multiple layers, R-values add in series.
Worked Example
10 cm of fiberglass insulation (k = 0.04 W/(m·K)).
- 01R = d / k
- 02R = 0.1 / 0.04
- 03R = 2.5 m²·K/W
Frequently Asked Questions
How do R-values add up?
For layers in series (like wall construction), R-values add directly: R_total = R1 + R2 + R3. This is similar to resistors in series.
What does R-value mean on insulation packaging?
It indicates thermal resistance per unit area. Higher R-value means better insulation. R-19 is typical for walls; R-38 to R-60 for attics.
What is the difference between R-value and U-value?
U-value is the reciprocal of R-value (U = 1/R). Lower U-value means better insulation. U-value is commonly used in building codes outside North America.
Ready to run the numbers?
Open Thermal Resistance Calculator