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openstudio output problem

asked 2015-02-07 06:28:39 -0600

eldav gravatar image

updated 2017-07-22 10:06:07 -0600

I have a simple model with an exterior window. I use Radiance for daylighting simulation. I run the baseline model (south orientation) and different orientations (45, 90, 180, ...) with PAT. Every time I run the same model, the values that I receive for "zone lights total heating energy" is different ! For example it changes from 300 kWh to 420 kWh for the same model. Even if I run the model with OpenStudio Application instead of PAT for one of the models, the value of the output is not the same! what is the reason and how can I be sure which results are correct?


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answered 2015-02-07 09:10:08 -0600

If you are getting different values for "zone lights total heating energy" when you rotate the building, my guess is that some of your lights are controlled by a daylight sensor. When you rotate the building, it changes how much daylight comes through the windows in the zone. In orientations where more daylight comes through the windows, the daylight sensors dim the electric lights more, leading to a reduction in "zone lights total heating energy."

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answered 2015-02-07 11:01:38 -0600

eldav gravatar image

Yes, I have a daylighting sensor in the zone but the difference in values occurs for the same orientation each time (for example South). when I run the model two or three times for south or north or ..., each time I receive different values for a specific orientation and this difference occurs for all of the orientations. when I run the model with another window construction (clear 6mm), every time I run the model for a specific orientation, I receive the same values and it is ok. The problem happens when I use a glazing material with these properties: Visible transmittance: 0.075 Solar transmittance: 0.065 Visible reflectance (front side): 0.293 Visible reflectance (back side): 0.554 Solar reflectance (front side): 0.243 Solar reflectance (back side): 0.553 emissivity: 0.84 In this case, the Schedule Compact fields has more than 6000 fields! (this schedule is made by radiance and pass to EnergyPlus). But this should not make any difference in the results by running the model each time.

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Based on your description it sounds like there might be an order-dependent issue with the osm to Radiance translator, not something you are doing wrong. @rpg777 can you get this model and take a look?

aparker gravatar image aparker  ( 2015-02-07 12:23:04 -0600 )edit

how can I fix this problem? Which model should I get and take a look from the link you sent?

eldav gravatar image eldav  ( 2015-02-07 12:58:43 -0600 )edit

I think it might be a problem inside OpenStudio, in which case the OpenStudio developers will need to fix it. You could try using EnergyPlus as the daylighting engine for now. If you can put the file on dropbox or something and post a link here, we can look into the issue.

aparker gravatar image aparker  ( 2015-02-07 13:09:22 -0600 )edit

I don't believe any of the Radiance stuff has been tested with PAT. Sounds like a great opportunity to do so, though. @eldav, as @aparker suggests, could you post your model someplace where we could pick it up and check it out?

rpg777 gravatar image rpg777  ( 2015-02-10 10:10:15 -0600 )edit

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Asked: 2015-02-07 06:28:39 -0600

Seen: 241 times

Last updated: Feb 08 '15