Input Data
Example Data Table
| Case | Inside Temp (°C) | Outside Temp (°C) | Area (m²) | Layer Stack | Total Resistance (m²·K/W) | U-Value (W/m²·K) |
|---|---|---|---|---|---|---|
| Office Wall | 24 | -2 | 12 | 100 mm Brick + 50 mm Insulation + 20 mm Plaster | 1.611746 | 0.620445 |
| Cold Storage Panel | 5 | 35 | 18 | 0.6 mm Steel + 80 mm PU Foam + 0.6 mm Steel | 3.406848 | 0.293526 |
| Concrete Envelope | 22 | 40 | 20 | 15 mm Plaster + 150 mm Concrete + 20 mm Finish | 0.355238 | 2.815597 |
Formula Used
Composite wall heat transfer uses a thermal resistance network. Each resistance is added in series. The heat flux follows the overall temperature difference.
Layer resistance: Rlayer = L / k
Film resistance: Rfilm = 1 / h
Total resistance per unit area: Rtotal = ΣR
Heat flux: q = (Tinside - Toutside) / Rtotal
Heat transfer rate: Q = q × A
Overall U-value: U = 1 / Rtotal
Interface temperature drop: ΔTi = q × Ri
This method supports multilayer wall assemblies with optional inside and outside convection films.
How to Use This Calculator
- Enter indoor and outdoor air temperatures.
- Provide the wall area for the assembly.
- Choose how many solid layers are active.
- Enter each layer name, thickness, and conductivity.
- Keep film resistance enabled for realistic boundary conditions.
- Click Calculate Heat Transfer to view results above the form.
- Use CSV or PDF download buttons to export calculated output.
Engineering Notes
- Low conductivity materials increase thermal resistance quickly.
- Thin metal sheets add little resistance unless insulation exists.
- Surface films can materially affect low-resistance wall systems.
- High U-values indicate faster heat transfer through the wall.
- Interface temperatures help assess condensation risk zones.