Question-and-Answer Resource for the Building Energy Modeling Community
Get started with the Help page
Ask Your Question

Difference in Window Area between EnergyPlus and OpenStudio DOE Prototype Buildings

asked 2016-07-16 15:00:01 -0500

updated 2016-07-19 10:45:48 -0500

Hello, I used OpenStudio (v. 1.12) and ran the measure 'Create DOE Prototype Building' to create an ASHRAE 90.1-2010- SmallOffice building in climate zone 2A. The results are shown below:

Overall energy use: image description

End energy use:

image description

I then proceeded to download and run the equivalent 90.1-2010 EnergyPlus model from the Commercial Prototype Building Models website in EnergyPlus version 8.5. The EnergyPlus results are shown below:

image description

Although the overall results are fairly close (201.99 GJ vs 203.18 GJ is less than 1% difference in total site energy), it appears that the individual end use loads vary quite a bit. The cooling is 27% higher (41.71 GJ vs 30.33 GJ) in the EnergyPlus prototype and the lighting is 20% less (53.89 GJ vs 65 GJ) in the EnergyPlus prototype.

Since the cooling load increased and lighting decreased, my suspicion was that the WWR might be different between the two prototype buildings and it is.The southern WWR in the EnergyPlus prototype building is 24.44%, while the OpenStudio version is 19.81%. Why is there a difference between these models window-to-wall ratios? Are there any other differences between the prototype buildings that I should be wary of?

edit retag flag offensive close merge delete



This looks like a bug in the OpenStudio implementation. I filed an issue. Thanks.

__AmirRoth__'s avatar __AmirRoth__  ( 2016-07-17 10:06:05 -0500 )edit

No problem! I will fool around a bit with the WWR of the south wall of the OpenStudio version and see if any other errors pop up.

Jonny K's avatar Jonny K  ( 2016-07-17 11:22:29 -0500 )edit

It appears that the fault might be a difference in the the Southern Door between the EnergyPlus model and the OpenStudio model. The EnergyPlus prototype uses a 'glass door' while the OpenStudio prototype version uses a non-glass door (Typical Insulated Metal Door R-1.43). It appear this is the case for other SmallOffice buildings in other climate zones as well. I'm not sure if this was a conscious decision or which model would be a more accurate representative of an ASHRAE 90.1-2010 SmallOffice building. I'll see if other building types also have this same issue.

Jonny K's avatar Jonny K  ( 2016-07-17 12:00:16 -0500 )edit

The OpenStudio models were/are intended to be replicas of the EnergyPlus models. This will be fixed. Thanks for identifying it.

__AmirRoth__'s avatar __AmirRoth__  ( 2016-07-17 13:35:08 -0500 )edit

1 Answer

Sort by ยป oldest newest most voted

answered 2016-07-19 09:27:21 -0500

updated 2016-07-19 10:45:16 -0500

@__AmirRoth__ 's answer (this is a bug) is correct. Here's some background for other people who run across this question. The OpenStudio versions of the DOE Prototype/Reference buildings are a work-in-progress. We released them for general use because the overall results numbers are reasonable, but there are some known and unknown differences between the OpenStudio versions and the original IDF versions that we're still working to reconcile.

Known differences:

  • The original files are in E+ 7.2 (Reference) and E+ 8.0 (Prototype) vs. E+ 8.5 for the OpenStudio models
  • Daylight sensor placement is slightly different
  • Minimum VAV damper positions are slightly different in some cases (impacts models with VAVs)
  • OpenStudio versions don't yet incorporate EMS from original IDF files
  • Infiltration for doors hasn't been added (impacts small buildings most significantly)
  • Possible minor mistakes were found and corrected in original IDF files

Unknown differences:

  • (just kidding)

If you find additional issues, please report them here.

We'd rather have false alarms than miss things, so if you find actual or suspected issues, please report them.

edit flag offensive delete link more



If there was a way to give two bumps -- one for the answer and one for the Rummy-joke embedded within it -- I would.

rpg777's avatar rpg777  ( 2016-07-19 10:19:11 -0500 )edit

Personally, I would actually dock for Rummy quotes.

__AmirRoth__'s avatar __AmirRoth__  ( 2016-07-19 10:44:20 -0500 )edit

Speaking of, I just noticed that upvote is red and downvote is blue! What's up with that? Shouldn't it be the other way around?

__AmirRoth__'s avatar __AmirRoth__  ( 2016-07-19 10:45:03 -0500 )edit

Your Answer

Please start posting anonymously - your entry will be published after you log in or create a new account.

Add Answer

Training Workshops


Question Tools

1 follower


Asked: 2016-07-16 15:00:01 -0500

Seen: 584 times

Last updated: Jul 19 '16