How to Calculate Window Heat Loss
What is Window Heat Loss?
A window heat loss calculator estimates the thermal energy lost through windows based on their U-value (thermal transmittance), area, and the temperature difference between inside and outside.
Formula
Step-by-Step Guide
- 1Heat loss (W) = U-value × Area (m²) × ΔT (°C)
- 2U-value: single glazing ~5.8; double ~2.8; triple ~1.1 W/m²·K
- 3ΔT = Indoor temp − Outdoor temp (°C)
- 4Annual heat loss (kWh) = W × Hours/season / 1,000
Worked Examples
Frequently Asked Questions
What is Window Heat Loss?
A window heat loss calculator estimates the thermal energy lost through windows based on their U-value (thermal transmittance), area, and the temperature difference between inside and outside. Use this calculator for accurate, instant results.
How accurate is the Window Heat Loss calculator?
The calculator uses the standard published formula for window heat loss. Results are accurate to the precision of the inputs you provide. For financial, medical, or legal decisions, always verify with a qualified professional.
What units does the Window Heat Loss calculator use?
This calculator works with inches, square metres, Celsius, kilowatts. You can enter values in the units shown — the calculator handles all conversions internally.
What formula does the Window Heat Loss calculator use?
The core formula is: Heat loss (W) = U-value × Area (m²) × ΔT (°C). Each step in the calculation is shown so you can verify the result manually.
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