Wall Heat Loss Calculator
Conduction heat flow through any envelope element: Q = U·A·ΔT.
The fundamental envelope equation. Sum it over every wall, roof, window and floor and you have a manual heat-loss calculation — element by element.
Formula
Wall Heat Loss Calculator is a free heat loss wall for HVAC designers, technicians and energy auditors — instant, accurate and 100% client-side, with the governing formula and reference shown next to the result so the number can be defended, not just quoted.
About Wall Heat Loss Calculator
Conduction heat flow through any envelope element: Q = U·A·ΔT. The calculation implements Q = U·A·ΔT (ASHRAE Fundamentals; ISO 13789). The fundamental envelope equation. Sum it over every wall, roof, window and floor and you have a manual heat-loss calculation — element by element.
How to use Wall Heat Loss Calculator
- 1Enter U-value in W/m²K.
- 2Enter Element area in m².
- 3Enter Temperature difference in °C.
- 4Read Heat loss, Daily energy at this ΔT instantly — no submit button needed.
- 5Need US units? Flip the SI/Imperial toggle and every field converts.
Why use Wall Heat Loss Calculator?
- ✓Implements the standard formula — Q = U·A·ΔT
- ✓Reference cited on-page: ASHRAE Fundamentals; ISO 13789
- ✓One-click SI ⇄ Imperial toggle — values convert in place, physics stays in SI
- ✓Live worked example: the substitution recomputes from your numbers
- ✓Runs entirely in your browser — nothing uploaded, free forever
Frequently asked questions
What formula does the Wall Heat Loss Calculator use?+
It computes Q = U·A·ΔT, per ASHRAE Fundamentals; ISO 13789. The formula is displayed under the result along with a worked example substituted with your own inputs.
What should I keep in mind when using this calculator?+
The fundamental envelope equation. Sum it over every wall, roof, window and floor and you have a manual heat-loss calculation — element by element.
Is this based on ASHRAE methods?+
The calculations follow the standard ASHRAE/ISHRAE formulations cited under the result, simplified where industry practice does the same. For permit-grade design, confirm with the full code procedure.
Is the Wall Heat Loss Calculator free to use?+
Yes — completely free, no sign-up, no limits. It runs client-side in your browser, so inputs stay private and results are instant even on slow connections.
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