Calculator Inputs
Formula Used
Rlayer = L / k
Rtotal = Rsi + ΣRlayer + Rso
U = 1 / Rtotal
q″ = ΔT / Rtotal and Q = A × ΔT / Rtotal
Rimperial = 5.678263337 × Rmetric
Here, L is layer thickness in meters, k is thermal conductivity in W/m·K, A is area in square meters, and ΔT is the temperature difference between indoors and outdoors. A higher R-value means better resistance to heat flow, while a lower U-factor means better insulation performance.
How to Use This Calculator
- Enter the surface area being analyzed.
- Provide indoor and outdoor temperatures to define the temperature difference.
- Select a suggested surface preset or keep custom values.
- Enter inside and outside surface resistances.
- Add each material layer with thickness and conductivity.
- Use a custom R override when a datasheet already gives layer resistance.
- Click the calculate button to view total R-value, U-factor, heat flux, and heat loss.
- Download the results as CSV or PDF after calculation.
Example Data Table
| Material | Thickness (mm) | Conductivity (W/m·K) | Calculated R (m²·K/W) |
|---|---|---|---|
| Gypsum Board | 12.5 | 0.170 | 0.0735 |
| Mineral Wool | 100 | 0.040 | 2.5000 |
| Brick | 100 | 0.770 | 0.1299 |
| EPS Board | 50 | 0.036 | 1.3889 |
| Plywood | 18 | 0.130 | 0.1385 |
These values are example inputs for demonstration. Always confirm actual product data from the manufacturer.
FAQs
1. What does R-value mean?
R-value measures resistance to heat flow. Higher values mean the assembly slows heat transfer more effectively, which usually improves insulation performance.
2. What is the difference between R-value and U-factor?
They are inverses. R-value describes resistance to heat flow, while U-factor describes how easily heat passes through the assembly.
3. Why are surface resistances included?
Surface films add small thermal resistances at the inside and outside faces. Including them gives a more realistic total assembly resistance.
4. Can I enter a custom layer R-value directly?
Yes. Use the custom R override when a datasheet already provides a tested layer resistance. That value takes priority over thickness and conductivity.
5. Does a thicker material always raise R-value?
Usually yes, if conductivity stays the same. Greater thickness gives more resistance, which lowers heat transfer through that layer.
6. Why does low conductivity improve insulation?
A lower conductivity value means heat moves through the material more slowly. That increases resistance and improves insulation quality.
7. Can this calculator be used for walls, roofs, and floors?
Yes. It works for any layered building assembly. Just enter the correct area, temperatures, surface resistances, and material data.
8. What units does this calculator return?
It returns metric thermal resistance in m²·K/W, imperial R-value in ft²·°F·h/BTU, U-factor in W/m²·K, and heat loss in watts.