weather file vs design day file in openstudio

answered 2015-11-13 11:29:17 -0600

The DDY file is used for zone/system/plant sizing (design day simulation), while the EPW file (typically including hourly data for a year) is used for annual (a period) energy simulation.

The DDY file is in IDF format. You can copy and paste the objects in DDY file to IDF file.

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Thank you very much!

SVVitale ( 2015-11-13 13:41:58 -0600 )edit

So is it possible that I only import a DDY file for system sizing but import no EPW file?

W. Chiang ( 2017-04-16 08:36:43 -0600 )edit

@W. Chiang, Yes. You can import DDY file for system sizing without the EPW file. You need to modify the SimulationControl object as follow:

SimulationControl,

Yes, !- Do Zone Sizing Calculation

Yes, !- Do System Sizing Calculation

Yes, !- Do Plant Sizing Calculation

No, !- Run Simulation for Sizing Periods

No; !- Run Simulation for Weather File Run Periods

Yixing Chen ( 2017-04-17 19:51:39 -0600 )edit

Thank you. I have another question, what's the difference between zone sizing and system sizing? I created a building with a single zone, and the design sensible cooling load in System Sizing I've got is roughly two times the size of the design sensible cooling load in Zone Sizing.

W. Chiang ( 2017-04-18 22:44:37 -0600 )edit

This probably means you have a system serving multiple zones.