Why heat gain through opaque surfaces and windows is zero on some days in energy plus result

asked 2019-04-03 05:18:17 -0500

while simulating some projects I found that Zone Opaque Surface Inside Face Conduction GainW on 21st of 5th month at 15:00 hrs is showing zero and similar case happens for windows too. Is this right? as for heat loads I need these values and I think they should not be zero

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Is this only for this 15:00 timestep, or does it occur at multiple times on that day? Is this a design day, or part of an annual simulation? Is this an interior surface touching an adjacent zone, or an exterior surface touching outdoor air?

Zero conduction should only happen if a surface's outdoor face temperature (adjacent surface temperature, outdoor air temperature, etc.) is exactly equal to the same surface's indoor face temperature. This is more likely to occur for two interior zones touching each other with the same thermostat settings, but still rare.

Aaron Boranian gravatar image Aaron Boranian  ( 2019-04-03 15:37:46 -0500 )edit

This is not only for !5:00 Hrs it occurs at multiple times in design day report and even in an annual report. Some surfaces are interior but all the outer surfaces are exposed to the Sun.

Pratik gravatar image Pratik  ( 2019-04-04 06:30:02 -0500 )edit

I should have mentioned that the Zone Opaque Surface Inside Face Conduction Gain output variable is the SUM of conduction through all surfaces into a zone. So, if the output is zero then all conduction going into the zone is equal to all conduction going out of the zone. I would recommend adding ...

Aaron Boranian gravatar image Aaron Boranian  ( 2019-04-04 11:02:20 -0500 )edit

Surface Inside Face Conduction Heat Transfer Rate output variables to confirm that the pos and neg conduction values are equal for the same timesteps where you see zero zone conduction. I would also recommend adding screen shot images to your post to indicate where in the output file(s) you are seeing zero zone conduction. The annual report might show zero if you are only running design days and not run periods with EPW weather.

Aaron Boranian gravatar image Aaron Boranian  ( 2019-04-04 11:04:08 -0500 )edit

I would also recommend adding energy monitor for specific window(s). Like this: Output:Variable,WindowNameHere,Surface Window Heat Gain Energy,Hourly;

vidanovic gravatar image vidanovic  ( 2019-04-04 12:12:14 -0500 )edit