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Zone loads instead of HVAC loads in OpenStudio or EnergyPlus

asked 2021-08-31 17:38:27 -0500

gcampos's avatar

updated 2021-09-01 11:42:29 -0500

Hi all,

Does anyone know how to get hourly loads (heating and cooling) for each zone, instead of for the HVAC equipment or facility (as reported by default in the reports)? For example, my issue is that a single AHU distributes air at one temperature (usually cooled) to multiple VAV boxes in each zone, in which the air is (re)heated up to the required zone temperature. I need the actual loads for each zone, instead of how much heating and cooling the HVAC systems produced, since this cooling-reheating procedure "wastes" more energy than if you were cooling or heating each zone individually.

I am currently trying to get these variables using OpenStudio's "output variables" tab, but I can't seem to find them. The closest I got was a variables called "Output:Variable,*,Zone Air System Sensible Heating Energy,hourly; !- HVAC Sum [J]", but the HVAC sum part is worrying me that e+ is getting this variable from the HVAC side.

Any help is appreciated. Thanks in advance!

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answered 2021-09-01 10:43:03 -0500

OpenStudio application-> OpenStudio Results-> Zone Overview-> Zone Sensible Cooling and Heating Sensible Sizing. This shows calculated sensible design loads for heating and cooling as well as design loads with any sizing factor that was use in the simulation settings tab.

You can also find this information in the EnergyPlus Results-> Initialization Summary-> Zone Sizing Information.

The values on these tables represent the actual zone sensible load and do not include external inefficiencies (ie. motors, fans, coils, compressors, etc.) or heating/cooling of ventilation air.

If you want to know the latent values, you will have to use the output variable "Zone Total Internal Latent Gain Rate". Alternatively, you can also use the output variable "Zone Total Internal Total Heating Rate" to see the total sensible+latent.

The EnergyPlus Input Output Reference manual ( gives a detailed description of these on page 264.

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If you want hourly values, you will need to use the output variables as described above. The default reports only show peak load.

Ski90Moo's avatar Ski90Moo  ( 2021-09-01 17:00:20 -0500 )edit

Thanks @Ski90Moo for the info and for the quick update on the hourly values. I'm taking the time to look carefully into the variables you suggested.

gcampos's avatar gcampos  ( 2021-09-02 10:49:10 -0500 )edit

@gcampos you might find this thread helpful as well:

Ski90Moo's avatar Ski90Moo  ( 2022-05-13 11:36:23 -0500 )edit

Hi @Ski90Moo I added the "Zone Total Internal Latent Gain Rate" and the "Zone Total Internal Total Heating Rate" to my OpenStudio Measure, but I cannot find where the data is being outputted. Do you know where I can the output of these OpenStudio Measures?

IanVG's avatar IanVG  ( 2023-10-30 18:19:53 -0500 )edit

The output variables are included in the .sql file. You can use Data Viewer to visualize and export these to a spreadsheet:

Ski90Moo's avatar Ski90Moo  ( 2023-11-06 14:02:43 -0500 )edit

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Asked: 2021-08-31 17:38:27 -0500

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Last updated: Sep 01 '21