I see a minor difference between the model input of the window u-values and what has been reported in html file. Is there any reason for such difference or am I missing sth here?
Thanks
The U-value used by EnergyPlus is not the same as the one you input. EnergyPlus calculates an effective U-value that attempts to interpolate between the input SHGC/U indices, in order to approximate the interaction of radiation and temperature through the window layers. It then constructs a equivalent detailed window model with a single layer with those properties.
It looks like you’re hitting the maximum effective U-factor limit during this effective U-value calculation process:
From Engineering Reference documentation on effective U-value calculation here: Window Calculation Module: Engineering Reference — EnergyPlus 9.6
Note: As far as I can tell, both the _u_factor HB input and the calculated “Glass U-Factor” output from EnergyPlus incorporates air films, so the difference is not due to any mismatch there.
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