Title-24 Prototype Models

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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?

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.