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How much variance between an OpenStudio model versus an eQuest model?

asked 2015-01-28 08:13:04 -0600

updated 2015-07-10 20:52:45 -0600

We're working on a small residence for a private school, and used eQuest for an initial model, with the intent to use OpenStudio for the final model submission in a few months. We have not submitted a model using OpenStudio before (and I'm really the only who has done any E+ work at our company).

The building has a number of features in it (VRF, DOAS, indirect water heating, external enclosure for VRF compressors) which aren't well modeled in eQuest, and required a number of workarounds which to me seem at best, grossly inaccurate.

My question is how much variance should be expected between the two models? Does anyone have experience with comparing the two engines and have an idea about where differences should be expected?

Currently, the lighting, equipment, and DHW are fairly well in line, with some variances due to how the buildings were specified within each software. These are fairly easily explainable. Where the problems are arising are with the fan and pump energy, as well as heating and cooling energy.

Any insights anyone has with comparing these two software packages would be very helpful.

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This link has a comparison spreadsheet between the two proposed models, eQuest versus E+ (click on the Graphs tab to view the comparisons between the various end uses). I can explain away the differences in everything except fan energy and cooling (where the largest variances exist).

I'm actually inclined to favour the E+ results over the eQuest results in this case.

Benjamin's avatar Benjamin  ( 2015-02-11 13:52:48 -0600 )edit

@Benjamin Your Dropbox link is dead. Was that intentional?

Jamie Bull's avatar Jamie Bull  ( 2015-07-27 09:01:25 -0600 )edit

Are there any updates to this question? I would love to see the resulting comparison, if it was completed.

Anna Osborne Brannon's avatar Anna Osborne Brannon  ( 2018-09-05 21:25:26 -0600 )edit

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answered 2015-01-30 09:34:17 -0600

In my experience in comparing OS models to eQuest models it seems like OS results in slightly less (~10%) HVAC energy consumption when compared to a similar system in eQuest. Now this is just a estimation from having several projects with an eQuest and OS models. This could be for hundreds on reasons, and I have not spent the time to try to figure out exactly why this has been the case in the models I have seen.

Lighting and plug loads should line up perfectly due to the energy use from these only being influenced by the load and schedule, like you mentioned above.

I could not predict how the total HVAC energy use in your eQuest and OS model will turn out. HVAC loads are met differently in the two programs, not to mention different curves and often times different inputs for the exact same system between the two. Due to the complexity of the system, and the fact you used workarounds in eQuest, to be able to predict which model will use more energy would be very difficult.

When you have completed both models I would be very interested in the comparison and it would be great if you could follow up with the community here on Unmet Hours.

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I certainly will post an update when the models are finalized. We are still trying to nail down the proposed in eQuest, because eQuest simply wasn't built to model this kind of building and the systems that are being installed.

I have a couple of comparison spreadsheets for both the proposed and reference buildings to compare between eQuest and E+ that I will post up when I get a chance, just to maybe stimulate the discussion.

Benjamin's avatar Benjamin  ( 2015-01-30 10:05:15 -0600 )edit

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Asked: 2015-01-28 08:13:04 -0600

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Last updated: Feb 11 '15