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[EnergyPlus_Support] Surface heat flux interpretation

Hello,

Looking to a surface heat transfer I can't understand how heat flux is computed.

In Winter Design Day calc (T out = -3.1°C, T int = 22°C).
The U value surface-to-surface is 1 (one layer with a R=1 material only). My wall is 82.07 m2.

Convection algorithms are Simple for interior and exterior. I set no wind so that U convection int and out are those expected (Uc int = 3.076, Uc out = 8.23). At surface level output show me these values.

Now if I try to manually calculated heat transfer using convection given by outputs I can't get the Heat loss calculated by E+.
E+ give me 1194 W when I find 1434 W.

Where am I wrong?
May be this formula is not complete, does E+ uses another equation?
Heat = U-value-with-film x Surface x (T int - T out)

Thanks for any tip




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