Is the OnIfHighSolarOnWindow shading control type too low to be useful?

asked 2018-10-23 22:21:03 -0600

updated 2018-10-24 14:57:14 -0600

This value seems to be un-editable in the OpenStudio interface and does not seem to even appear in the .osm file (?). The value can be found in the .idf file. Here it is expressed as 27 (presumably W/m2). Which means that anytime incident solar radiation is greater than 27 W/m2, shades, blinds, or darker glazing are deployed. At this threshold how is this useful? Minimum radiation during daylit hours on East, South, and West facades in most locales are substantially higher than this, meaning that shades may as well be scheduled to be down during the day and up at night. Am I missing something? Are the units not actually W/m2?

Thanks! image description

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answered 2018-10-24 10:56:38 -0600

rpg777
6970 ●6 ●15 http://openstudio.net/

It's in there somewhere (OSM)! It's not editable from the App interface, but you can edit it in the SketchUp plugin (inspector); OS:ShadingControl(s) are listed there and you can edit the setpoint.

27 W/m^2 works out to about 500 lux (I need to think in terms of visible), which is conservative, but definitely not tantamount to saying the shades are always down. In testing, we found that this setpoint would trigger the blinds on "bright overcast" day, which again is conservative but does happen in RealLife[TM]. It's a long way from realistic, and there is no stochastic element to the blind activation (speaking for the Radiance measure), but it's better than always down (and always up!).

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Is there a suggestion here that could improve shade/blind controls in E+?

rraustad ( 2018-10-24 11:04:18 -0600 )edit

Ph.D. thesis, more like.

rpg777 ( 2018-10-24 11:22:18 -0600 )edit

The setpoint is already an input in EnergyPlus so you should be able to access that by writing an OpenStudio measure.

JasonGlazer ( 2018-10-24 11:27:49 -0600 )edit

@rpg77 thanks for the feedback! I have no problem finding it in the IDF (image above), but no matter what I search I can't seem to find the actual value in the OSM! (I am able to find reference to the shading control type "OnIfHighSolarOnWindow" though). Anyway...the important part is that I can edit it somehow, so thanks for that.

And yes, you're right. Further assessment of the local climate data for my site suggests that 27 W/m2 is very conservative, but not so much so that shades will always be deployed - thought it seems that they will be for nearly all day hours on the south facade.

jbatt ( 2018-10-24 15:05:17 -0600 )edit

If no setpoint value is in the OSM, it appears to automatically get set to 27 for this shading control type here: https://github.com/NREL/OpenStudio/bl...

shorowit ( 2018-10-24 18:20:09 -0600 )edit

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Is the OnIfHighSolarOnWindow shading control type too low to be useful?

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Is the OnIfHighSolarOnWindow shading control type too low to be useful?