Shading not being applied

shading
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Hi.

I am looking for a tutorial/info/posts on fixed site/building/space shading. This is a very basic question because this is my first OS model and so far I am not able to get the shades in my model to work (i.e. some shades are applied to the building and some are applied to spaces but none have any impact (deleting the shades has the same result).

I suspect the problem is something to do with schedules or transmittance settings (which I am still learning about also) but I haven't yet found guidance.

Thanks, Paul

Paul Graham

asked 2016-08-03 15:37:29 -0500

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__AmirRoth__

updated 2016-08-03 15:46:19 -0500

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Are the shading devices showing up as purple in your model? Or are they white? If they are white, they are not part of the OpenStudio model, they are just SketchUp surfaces.

__AmirRoth__ (2016-08-03 15:52:04 -0500) edit

Thanks. Shades are purple on building and blue in group. These are simple fixed permanent shading overhangs. I think I have the basics correct from the tutorials etc; so am after more detailed tutorials etc on shading setup. I thought just placing the shades in shading groups in Sketchup would work, but they have no effect. I believe the problem is my setup in OS rather than Sketchup (perhaps scheduling or transmittance). I read the error file prior to my first post and it said shades were always transparent so I amended models and no such error now but still no effect. Regards, Paul

Paul Graham (2016-08-04 19:40:47 -0500) edit

Try reporting fraction sunlit for the surfaces that are supposed to be shaded.

David Goldwasser (2016-08-07 08:45:08 -0500) edit

Thanks David. I cant see how to report fraction sunlit. The main zone and shade in my model only has East glass and I reported "zone windows total trans'd solar radiation". This indicates no shading in the model (solar indicates sun on windows from sunrise to noon but hand calc shows no sun on windows after 10am), also energy is same if shades are in the model or deleted. I tried various transmitance schedules; using on(1)/off(0) trans schedule (for example) there is a tiny difference - this indicates to me that it is likely transmittance is the problem. However, I cant find how to fix this.

Paul Graham (2016-08-07 23:17:37 -0500) edit

I might have to see the file. Are you trying to do something with a transmission schedule? If you want it be opaque all of the time, you don't need to associate a schedule with a shading surface. Another possible cause would be if the shading surface was inverted, but that shouldn't typically be an issue since (unless you are adding PV) since EnergyPlus mirrors shading surface by default, unless you disabled that.

David Goldwasser (2016-08-08 08:58:00 -0500) edit

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The EnergyPlus Results Report includes a Shading Summary image description

OpenStudio doesn't write the shading objects in the same way that Design Builder does. I recall looking through a DB file and finding a Shading Schedule for every shading surface.

You can convince yourself of that by looking at the out.idf in the sub directory of your working folder. e.g. ..\Your model folder\run\4-EnergyPlusPreProcess-0\out.idf

The Shading Report is a direct way of checking the effect of shading. (Annual) Energy consumption and or cross checking with hand calculations may not be precise enough to conclude that the Shading in your model is ineffective.

Perhaps also look at the few other Output variables

Zone Exterior Windows Total Transmitted Beam Solar Radiation Energy
Output:Variable,*,Surface Outside Face Sunlit Area,hourly; !- Zone Average [m2]
Output:Variable,*,Surface Outside Face Sunlit Fraction,hourly; !- Zone Average []

These links and resources took a bit of googling to find; - Look at the 'Add Output Variables' measure described here http://nrel.github.io/OpenStudio-user... - Downloading and applying measures is actually quite easy, despite the hoops to jump through when getting started, https://bcl.nrel.gov/node/37843

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TomB

answered 2016-08-14 17:48:03 -0500, updated 2016-08-14 23:34:50 -0500

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I also had the same problem. Answer: Go to E+ IDF editor, under simulation parameters go to building/solar distribution and set to FullInteriorAndExterior Mine was set to MinimalShadowing which only calculates shadowing for reveals. (refer to EnergyPlus OutputInput Reference document, item 1.4.4.1.7 Field: Solar Distribution on page 41). I am yet to verify but i am hoping this will also solve the problem i had of change glazing material type not having any effect.

Ngoni

answered 2019-06-21 03:46:45 -0500

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I have the same problem here. In the EnergyPlus Results Report the Surface Shadowing Summary shows the shading surfaces and the Possible Shadow Receivers, while Shading Summary shows none Sunlit Fraction.

It seem fixed by changing the number of timesteps per Hour to 6.