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"NR SBD Performance" calculation in Energy Pro

asked 2016-06-09 12:35:43 -0500

updated 2017-09-23 21:59:03 -0500

Hi all,

I have a technical question about Energy Pro specifically. Have anyone used "NR SBD Performance" Savings By Design non-compliance mode calc in Energy Pro before? I was trying to run Savings By Design calc to get the percentage of savings, but the result seems to be ridiculous. The results from "NR T24 Performance" calculation seems fine, it is showing about 15% better than Title 24 baseline, but the "NR SBD Performance" calculation results doesn't make sense to me at all, it became 28% worse instead. The fan energy use is ridiculously high.

I know that the Title 24 performance module uses CBECC-Com, how about SBD? The SBD only took 1 second to pop up the results for me..

Thanks for you help!

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@YC, is this a relatively small building? i.e below 10,000 sqft? The EnergyPro SBD module is both a different engine to CBECC-Com, but it also interprets and implements the ACM in a very different way than CBECC-Com leading to vastly different results at times.

pflaumingo's avatar pflaumingo  ( 2016-06-14 08:59:25 -0500 )edit

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answered 2016-06-22 11:13:49 -0500

updated 2016-06-22 11:14:10 -0500

No, the "NR SBD Performance" module does not use CBECC-Com. It used the standard EnergyPro DOE-2 engine. If you uncheck "delete temporary files after simulation is complete" in the calculations section, you can access the .bdl and .sim files to dive a bit deeper.

From my understanding, the "NR SBD Performance" module was created to follow the CPUC ruling that the SBD model must represent the actual performance of the proposed building. Therefore, this mode allows the user to specify schedules and plug loads and model system types not currently supported by CBECC-Com or the ACM.

The "standard" building is still created using Title 24 rulesets as in CBECC-Com, but follows the proposed building schedule and plug load inputs (and uses the DOE-2 engine, not EnergyPlus). The results are also still presented in TDV. I have not used this module extensively, or done a comparison between the two, but that amount of disparity sounds much too large. I would check any potential missing inputs, and review the .sim files (and add more reporting capability if necessary) to figure out what is wrong.

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Thanks, Anna. You are right, the SBD non-compliance mode uses DOE-2, and it even use DOE-2 for compliance mode as well, which shows a significant difference compare to E+ compliance mode. I haven't had a chance to look deep into this, but I was able to make it pass by fix some parameters. Your help is appreciated.

Yiyu Chen's avatar Yiyu Chen  ( 2016-06-29 00:16:18 -0500 )edit

Glad to help. Just to clarify for others- Title 24 Performance Compliance is always done through CBECC-Com which uses EnergyPlus. EnergyPro does not have a mode that would be approved for a permit submittal that uses DOE-2 for Title 24 Performance Compliance. The "NR Performance" and "NR 90.1 Performance" modules do use DOE-2, but these are not acceptable for Title 24.

Anna Osborne Brannon's avatar Anna Osborne Brannon  ( 2016-06-29 10:22:48 -0500 )edit

I'm having the same problem on multiple projects. Compliance result is 15-20% better than 2013 T-24 but without change any input, the SBD module result drops to -20-30%. May I ask what parameters you changed that help to fix the problem?

xchen's avatar xchen  ( 2016-08-02 19:13:20 -0500 )edit

answered 2016-08-09 11:00:41 -0500

xchen's avatar

Here are a few things that I found for a building with VAV system

1). the zonal input for heating capacity is for reheat coil under compliance calculation (energy+);

image description

but the .doe file in the SBD calculation shows the capacity is read as "baseboard" capacity, which was the case for previous version Energypro.

image description

After I delete all heating capacity at the zonal system in the Design Case, the TDV heating energy consumption is reduced by 70%.

2). VAV turndown ratio must be higher than the min ventilation requirement and the min exhaust under compliance calculation (energy+); but the .doe and .sim file show the VAV turndown ratio for all zones are 0.2. After I changed all VAV turndown ratio to 0.2 in the Design Case, the TDV fan energy is reduced by 35%.

That's what I observed from test runs.

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Asked: 2016-06-09 12:35:43 -0500

Seen: 1,318 times

Last updated: Aug 09 '16