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Secondary Daylight control ignored

asked 2017-07-17 16:04:44 -0500

gsuscalo's avatar

updated 2017-08-05 07:29:41 -0500

Hello all,

[currently using OS 1.14 on a Windows 10 computer]

I have a question about using the radiance daylighting capability measure, because I'm seeing some contradictory info about it online. On forum responses, it's stated that there's two daylighting controls. But when I run my OS model with the radiance measure, it sends a message saying that the 'secondary' daylighting control will be ignored, and I see this repeated in the instructions online ( My question is- are the secondary daylighting controls in fact ignored in the current version of OS/radiance I use (I have whichever radiance gets automatically installed w/ OS 1.14), and are they included/used in any newer versions of Openstudio?


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answered 2017-07-17 19:48:19 -0500

There are indeed two daylighting controls allowed in a zone and these controls can be assigned to different percentages of the zone's lighting load -- if using EnergyPlus. However, the Radiance measure that comes with OpenStudio, as stated in the warning messages and in the docs you reference, only respect the primary control.

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So to be sure I understand this correctly (from your response and some other threads):

-If I use the radiance measure, Openstudio does the daylighting simulation with radiance. But radiance will only use the primary daylighting control

-If I set up daylighting controls and don't use the radiance measure, OS will use the energyplus daylighting programs, which accepts both daylighting controls but has issues with transmitting daylight between spaces.

..So the question of which method to use boils down to which of these things I think is more important for my project.

Is this correct?

gsuscalo's avatar gsuscalo  ( 2017-07-25 10:13:02 -0500 )edit

That's correct, but I would argue that you've understated the "issues" EnergyPLus has WRT daylighting calculations; it's absolutely awful. But yes, that's the deal. You can use EnergyPlus and have terrible spatial resolution, inaccurate results, incomplete daylight metrics, and a host of other issues, but you can easily apply it to your whole building and get a result in a reasonable timeframe. Or, you can use Radiance and actually simulate the daylight moving through your space the way it would in real life[TM], better daylight metrics, more flexibility, vetted BSDF data for blinds, etc...

rpg777's avatar rpg777  ( 2017-07-25 10:24:05 -0500 )edit

...but have to wait a lot longer for your better results. And work with an incomplete controls implementation. And easily overwhelm your resources if you accidentally populate the entire building with Radiance simulation points. And still have work to do in the data visualization end of things, etc...

rpg777's avatar rpg777  ( 2017-07-25 10:25:59 -0500 )edit

Thanks. I think I have a decent idea of what my options are now.

gsuscalo's avatar gsuscalo  ( 2017-07-25 10:52:28 -0500 )edit

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Asked: 2017-07-17 16:04:44 -0500

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Last updated: Jul 17 '17