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Window Assembly U-Factor, SHGC in EnergyPlus

asked 2015-10-20 12:56:50 -0500

updated 2020-01-20 15:06:27 -0500

In a Energplus or OpenStudio model that uses glazing and frame and divider objects from Windows 6, how can you find the window's assembly U-Factor and SHGC? The eplustbl.htm gives the glazing and the frames U-Factors, but no assembly values. I dug through the input/output reference to try to find a output that would give me this, but couldn't find anything. Does anyone know in what output I can find this information?

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Can you get that from Window?

macumber's avatar macumber  ( 2015-10-20 13:29:41 -0500 )edit

Yes, but I have several different sized windows in my model. I don't want to have to build all of them in Window to find the U-Factor and to find a average U-Factor for all of the glazing.

TaylorRoberts's avatar TaylorRoberts  ( 2015-10-20 15:30:05 -0500 )edit

3 Answers

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answered 2015-10-20 17:17:11 -0500

updated 2015-10-20 17:19:01 -0500

EnergyPlus would have to perform a separate simulation of the window under NFRC testing conditions. I have been working on something for an ASHRAE project that does exactly this. This will come out as a standalone tool that we hope to integrate it into EnergyPlus sometime next year.

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Hi Neal, How about your project with ASHRAE? When do you expect that it i´ll be published?

luis melo's avatar luis melo  ( 2016-03-04 12:25:46 -0500 )edit

Heya Neal, a window assembly performance report would be very helpful! Is this still in the works?

TNZ Energy's avatar TNZ Energy  ( 2017-09-28 06:57:18 -0500 )edit

The ASHRAE project ended up not getting integrated into EnergyPlus proper. However, since then there has been a similar effort that should make this easier. You can follow the progress on GitHub, and the UserVoice request here.

Neal Kruis's avatar Neal Kruis  ( 2017-10-19 09:24:17 -0500 )edit

answered 2015-10-20 15:55:04 -0500

updated 2015-10-20 15:55:31 -0500

EnergyPlus does not calculate window assembly (glazing plus frame) U-factor or SHGC.

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I should probably know the answer to this, but ... given that WINDOW can calculate these and EnergyPlus essentially includes WINDOW (or whatever it's called now), why can't EnergyPlus do this?

__AmirRoth__'s avatar __AmirRoth__  ( 2015-10-20 16:00:45 -0500 )edit

@__AmirRoth__ If I am not wrong, As I understood form your comment,WINDOW software is included in Energyplus?

4Designer's avatar 4Designer  ( 2016-05-21 11:27:58 -0500 )edit

According to my understanding, EnergyPlus shares the calculation module with the WINDOW program. Maybe it doesn't share the entire module. Or maybe these functions are not exposed. @vidanovic would know the answer to this. Simon?

__AmirRoth__'s avatar __AmirRoth__  ( 2016-05-21 11:48:33 -0500 )edit

EnergyPlus does use thermal part of WINDOW engine for calculation. When using "standard" windows, EnergyPlus will use engine that is bit old (implemented around 2000), while using BSDF type of windows will use newer engine that is implemented around 2012. That engine does have SHGC and U-value calculations and that is reported in EnergyPlus output. However, report is only per windows construction and not for every window in a building. So if entire building uses same window construction then you should have only one window in report.

vidanovic's avatar vidanovic  ( 2016-05-21 12:48:49 -0500 )edit

Alos to update on current status (limit here is 600 characters so I did separate comment). LBNL is finishing new shared WINDOW engine module that is replacing current somewhat conflicting set of 3 different modules with the one that includes all of functionalities of WINDOW. This new shared engine will also provide NFRC style U, SHGC, VT, and CR as one of standard outputs. The new shared module is planned for inclusion in the next release of EnergyPlus.

vidanovic's avatar vidanovic  ( 2016-05-21 17:31:36 -0500 )edit

answered 2016-05-21 12:44:04 -0500

vidanovic's avatar

updated 2016-05-21 12:51:48 -0500

You should have U-value report only for certain constructions (center of glazings) and not for every window in the building. U-value of a window plus frame is not reported (and not calculated as such), however, I would need to check if that report is actually not part of eio file, but at a moment I am 99.99% sure that it is not. Note that U-value of COG is calculated by using standard NFRC conditions and not conditions from weather file that are used in simulation.

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Asked: 2015-10-20 12:56:50 -0500

Seen: 1,843 times

Last updated: May 21 '16