Wall Heat Loss
Calculator
Results
- Temperature difference (K)
- 26
- Heat loss (W)
- 312
- Energy lost (kWh)
- 7.488
- R-value (m²·K/W)
- 3.333333
Energy results
| Temperature difference (K) | 26 |
| Heat loss (W) | 312 |
| Energy lost (kWh) | 7.488 |
| R-value (m²·K/W) | 3.333333 |
formula-map diagram
- Temperature difference (K)
- 26
- Heat loss (W)
- 312
- Energy lost (kWh)
- 7.488
- R-value (m²·K/W)
- 3.333333
Energy relationship
Formula
Q = U × A × ΔT; R = 1 ÷ U= 26
Note
This is a simplified model: it applies the standard equation to the numbers you entered and ignores real-world losses, weather variation, tariff structures and equipment tolerances. Wind power assumes air density 1.225 kg/m³ at ISA sea level and the power coefficient you enter (Betz limit 0.593). Verify with measured data or a professional energy audit before making purchasing decisions.
More in Energy and environment
See all →Frequently asked questions
What does R-value or U-value represent in this calculation?+
R-value measures a wall's resistance to heat flow, so higher is better insulated, while U-value is its inverse, measuring how readily heat passes through, so lower is better. Heat loss calculations typically divide by R-value or multiply by U-value to get the rate of heat transfer per square foot or meter.
How is the heat loss rate calculated?+
Heat loss (in watts or BTU/hr) equals wall area times the temperature difference between inside and outside, divided by the wall's total R-value. A larger area, bigger temperature swing, or lower R-value all increase the calculated heat loss.
Why does adding insulation have diminishing returns?+
R-values add in series, so going from R-0 to R-10 cuts heat loss dramatically, but going from R-30 to R-40 saves proportionally less because you're already blocking most of the heat flow. Each additional layer of insulation reduces the heat loss rate by a shrinking percentage.
Does this calculation account for windows and doors in the wall?+
A basic wall heat loss calculation typically treats the wall as a single uniform material, so windows and doors, which usually have much lower R-values, need to be calculated separately and added to get the total heat loss for that wall section.
Why is my actual heat loss higher than the calculated value?+
Real walls have thermal bridging through studs, gaps in insulation, and air leakage at joints and penetrations, none of which a simple R-value calculation captures. These factors commonly add 10-30% more real-world heat loss than the theoretical figure.