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Title-24 Prototype Models

asked 2018-10-26 20:10:43 -0500

Ranjani gravatar image

updated 2018-10-27 12:39:19 -0500

How different are the CBECC-Com prototype models compared to DOE prototype model? I am using CBECC-com prototype (Large office)model and after running the model as-is without any changes, I get an EUI of 15.70 kBtu/hr/ft2. That seems very low compared to the DOE large office prototype model(EUI 60kBtu/hr/ft2). Is it to do with the just the standards alone(Title 24 Vs. ASHRAE)? Am I missing something? Have any of you seen the difference? Can I get some help on this? Thanks

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@Ranjani, Can you be more specific on how you got your results, including: - Which version of CBECC-Com you used (2016 or 2019, v3 SP2, v3 SP1, etc) - Which model you ran (file name) - What weather file was used, and was it consistent for both models? Keep in mind that CEC has funded development of it's own typical year weather files, which are not necessarily the same as TMY3 - Is the denominator in your calculation consistent and only includes conditioned floor area (the large office has both unconditioned parking, and plenum zones).

DavidReddy gravatar imageDavidReddy ( 2018-10-26 22:59:57 -0500 )edit

@DavidReddy I am using CBECC-Com 2016.3.0 SP1 version( I used LA as the location for my models. I used the Large office prototype. So the weather file could be the reason for the difference?

Ranjani gravatar imageRanjani ( 2018-10-26 23:15:59 -0500 )edit

@DavidReddy sorry I see the same .epw and .ddy files under CBECC-com weather files folder similar to what we have in OS/E+.

Ranjani gravatar imageRanjani ( 2018-10-27 21:32:01 -0500 )edit

2 Answers

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answered 2018-10-27 00:03:55 -0500

Assuming you are comparing to the 90.1-2016 prototype, and the CBECC-Com 040012-OffLrg-CECStd.cibd16 model, the biggest difference is the DOE prototype has a data center in the basement, where as the CBECC-Com model is parking garage. Beyond that, there are other differences in the code, and then also in how the systems are simulated. Weather I expect would result in a <5% difference.

I would expect the CBECC-Com EUI to be closer to 30 kBtu/SF. Can you post the results that you used to calculate the 15 EUI you mention?

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@DavidReddy Please find attached link to access the files. I extracted an OSM file from CBECC-Com Office Large Prototype Model. All I was trying to do is run a sizing run with the exported file in Openstudio and manually plug in the numbers in CBECC-Com and check to see if the building complies. Since CBECC-Com is not a sizing software, I decided to use Open Studio. But the EUI turned out to be close to 15 Kbtu/hr/ft2.

Ranjani gravatar imageRanjani ( 2018-10-27 21:25:57 -0500 )edit

@DavidReddy After doing the sizing runs in openstudio between two different glass types, I wasn't able to see any difference in HVAC sizing. Right now I am stuck, not sure whether to use CBECC-com protoype or creat DOE building in openstudio and match the building to CBECC-com. Here is the link to the model-

Let me know your comments. Appreciate the help. Thanks

Ranjani gravatar imageRanjani ( 2018-10-27 21:30:16 -0500 )edit

answered 2018-10-29 18:34:52 -0500

The easiest way to compare the two models is to compare the resulting EnergyPlus IDF files. CBECC-Com creates an IDF file for both the proposed and Title 24 baseline models in the "040012-OffLrg-CECStd - run" folder when a simulation is initiated ("040012-OffLrg-CECStd - ap.idf" and "040012-OffLrg-CECStd - ab.idf", respectively). Compare the baseline and/or proposed models to the DOE reference building IDF available here.

In general, the schedules, constructions, and system sizing/efficiencies are different, as well as the space type differences mentioned by DavidReddy. As DavidReddy also mentioned, the CEC weather files used in CBECC-COM are different from the standard DOE weather files.

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Asked: 2018-10-26 20:10:43 -0500

Seen: 237 times

Last updated: Oct 27 '18