Infiltration Heat Loss Calculator
Energy carried away by air leakage from ACH, volume and temperature difference.
The 0.33 is air's heat capacity per cubic metre per kelvin in watt-hours. In leaky homes infiltration rivals all conduction losses combined — caulk before you insulate.
Formula
Infiltration Heat Loss Calculator is a free infiltration heat loss 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 Infiltration Heat Loss Calculator
Energy carried away by air leakage from ACH, volume and temperature difference. The calculation implements Q = 0.33·n·V·ΔT (0.33 Wh/m³K = ρc_p of air) (CIBSE Guide A; ASHRAE Fundamentals ch. 16). The 0.33 is air's heat capacity per cubic metre per kelvin in watt-hours. In leaky homes infiltration rivals all conduction losses combined — caulk before you insulate.
How to use Infiltration Heat Loss Calculator
- 1Enter Building volume in m³.
- 2Enter Infiltration rate in ACH (Tight new build 0.2 · average 0.5–1 · leaky old 1.5+).
- 3Enter Temperature difference in °C.
- 4Read Infiltration loss instantly — no submit button needed.
- 5Need US units? Flip the SI/Imperial toggle and every field converts.
Why use Infiltration Heat Loss Calculator?
- ✓Implements the standard formula — Q = 0.33·n·V·ΔT (0.33 Wh/m³K = ρc_p of air)
- ✓Reference cited on-page: CIBSE Guide A; ASHRAE Fundamentals ch. 16
- ✓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 Infiltration Heat Loss Calculator use?+
It computes Q = 0.33·n·V·ΔT (0.33 Wh/m³K = ρc_p of air), per CIBSE Guide A; ASHRAE Fundamentals ch. 16. 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 0.33 is air's heat capacity per cubic metre per kelvin in watt-hours. In leaky homes infiltration rivals all conduction losses combined — caulk before you insulate.
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 Infiltration 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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