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eQuest simplified glass input method

asked 2015-07-22 11:15:52 -0500

jkjenner's avatar

updated 2015-11-11 13:02:15 -0500

I'm preparing a LEED EAp1/c2 model for which the construction documents specify glazing in terms of performance (i.e. U-value, SHGC, etc.). This makes inputting glass via the glass library tricky, as it basically amounts to reverse-engineering performance specifications. Much simpler would be entering these specifications directly using the "simplified" input mode, but I have heard rumblings here and there about this method being less accurate.

I'm wondering: what exactly is the difference, and how significantly will this affect model performance? Are there particular conditions under which using this input method might be more or less acceptable?

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answered 2015-07-22 16:31:01 -0500

updated 2015-07-22 17:26:00 -0500

The difference is largely in the angular dependent spectral properties (i.e., for non-normal solar angles). I don't know if this impact has been quantified anywhere. There is some discussion in this paper from LBNL.

There is work done in EnergyPlus to remedy this problem, but that too has its shortcomings.

You use the same methodology to build up a similar "Simple Glazing" system in BDL. I don't know if the objects are directly accessible from the eQuest interface. I implemented this in BEopt (when it still interfaced to DOE-2). You can potentially use an older version of BEopt to generate the BDL for windows given only a U-factor and SHGC.

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Asked: 2015-07-22 11:15:52 -0500

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Last updated: Jul 22 '15