Heat Loss Calculator
Enter the U-value, area and temperatures to find the heat loss.
Result
How to use
- Enter your values in the fields above.
- Press Calculate to see your result instantly.
- Use the Share button to copy a link to your result.
About this calculator
Steady-state heat loss through a building element follows a simple formula: Q = U × A × ΔT, where U is the element's U-value (thermal transmittance in W/m²K, lower is better insulated), A is its surface area, and ΔT is the temperature difference between inside and outside. Multiplying these gives the heat flow in watts leaving through that wall, roof, floor or window.
Architects and HVAC engineers sum this calculation across every wall, roof, floor and window of a building to size a heating system correctly, and energy auditors use it to identify which parts of a building's envelope are losing the most heat and would benefit most from added insulation.
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