Calculator Inputs
Use any material preset, or type a custom conductivity value.
Plotly Graph
This graph shows how heat loss rate changes as temperature difference increases.
Example Data Table
| Wall Type | Area (m²) | Thickness (mm) | k (W/m·K) | ΔT (°C) | U-Value (W/m²·K) | Heat Loss Rate (W) | Energy (kWh) |
|---|---|---|---|---|---|---|---|
| Brick Wall | 10.00 | 200 | 0.7200 | 17.00 | 2.2333 | 379.65 | 9.1117 |
| Concrete Wall | 14.00 | 180 | 1.7000 | 22.00 | 3.6247 | 1,116.42 | 13.3970 |
| Insulated Wall | 12.00 | 120 | 0.0400 | 23.00 | 0.3155 | 87.07 | 2.0896 |
| Wood Panel | 8.00 | 100 | 0.1200 | 12.00 | 0.9967 | 95.68 | 0.7654 |
Formula Used
Where:
- L is wall thickness in meters.
- k is thermal conductivity in W/m·K.
- Rsi and Rso are surface resistances.
- U is overall heat transfer coefficient.
- A is wall area in square meters.
- ΔT is the indoor to outdoor temperature difference.
- Q is heat loss rate in watts.
- E is total heat energy over the chosen time.
How to Use This Calculator
- Select a wall material preset or enter a custom conductivity value.
- Enter wall area and wall thickness.
- Type indoor and outdoor temperatures.
- Set the time duration for energy estimation.
- Adjust inside and outside surface resistances if needed.
- Click Calculate Heat Loss to see results.
- Review U-value, heat flux, heat loss rate, and energy totals.
- Use the export buttons to save the result as CSV or PDF.
FAQs
1. What does this calculator estimate?
It estimates conductive heat loss through a wall. It also shows wall resistance, total resistance, U-value, heat flux, heat loss rate, and energy used over a chosen time period.
2. Why is thermal conductivity important?
Thermal conductivity tells how easily heat moves through a material. Lower conductivity means stronger insulation. Higher conductivity means heat passes more quickly through the wall.
3. What is the difference between heat flux and heat loss rate?
Heat flux is heat transfer per square meter. Heat loss rate is the total heat transfer through the full wall area. Both values are useful, but they answer different design questions.
4. Why do surface resistances matter?
Surface resistances represent indoor and outdoor air film effects. They slightly reduce heat transfer and make the calculation closer to real wall performance under normal conditions.
5. Can I use Celsius for temperatures?
Yes. The calculator uses temperature difference, so Celsius values work perfectly. You only need consistent indoor and outdoor temperature units.
6. Does this include radiation or air leakage losses?
No. This tool focuses on steady conductive heat loss through the wall assembly. It does not include infiltration, thermal bridges, solar gain, or radiant exchange.
7. How can I reduce wall heat loss?
Use thicker insulation, lower conductivity materials, better air sealing, and improved wall assemblies. Reducing the U-value lowers heat loss for the same area and temperature difference.
8. When should I use a custom conductivity value?
Use a custom value when your wall material is not listed, or when manufacturer data provides a more accurate conductivity number for your specific product or design condition.