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Difference in volume calculated via sketch up and openstudio API

asked 2018-01-10 20:15:15 -0500

Karthick's avatar

updated 2018-01-15 10:08:02 -0500

I am using space.volume to get volume of a space. There is marked difference between the volume returned by space.volume and volume returned by sketch up. I have gone through previous questions in the forum. My geometry seems to be ok but it would be great to have a check. I load by model in sketch up and the plugin doesn't throw any reverse face warning messages. I have also rendered the model by Surface Normal and the whole model is white from the exterior. I have a very simple model with a zone and hip roof. The volume of the zone is right but volume of roof is incorrect. Please find the model attached and also screen shot below image description. I can provide a OSM file if anybody is interested in loading it up in sketchup. Please let me know, I can send it to you.

Sketch up value of volume - 7.33 cubic metre but space.volume gives me 8.57.

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@Karthick can you post your model?

Avi's avatar Avi  ( 2018-01-15 01:07:54 -0500 )edit

Any chance you have something other than planar surfaces in Sketchup that is taking up some volume?

bbrannon4's avatar bbrannon4  ( 2018-01-15 01:59:26 -0500 )edit

@Avi The whole OSM file will jumble up the question. Please send me your email id or email to me @ and I will respond to you with the OSM file.

Karthick's avatar Karthick  ( 2018-01-15 18:43:13 -0500 )edit

@bbrannon4 I don't understand your comment. Please clarify a bit more.

Karthick's avatar Karthick  ( 2018-01-15 18:44:09 -0500 )edit

@Karthick You can find my email in my profile

Avi's avatar Avi  ( 2018-01-16 02:01:39 -0500 )edit

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answered 2018-01-15 10:47:23 -0500

@Karthick have you checked what volume EnergyPlus calculates? There is a need to improve OpenStudio's volume calculations and also to make sure they agree with EnergyPlus's calculations. Couple of questions about the attic zone. Does it have a floor? Are the eaves modeled as shading surfaces?

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  1. I don't use energy plus at my work here. I only use opentstudio to store the OSM model and send it to chenauth for processing.
  2. The roof space has the roof slanting surfaces at pitch - 26.6 degrees and a roof base. All the surfaces in the roof space are of type roofceiling.
  3. Eaves are modeled as shading surfaces.
Karthick's avatar Karthick  ( 2018-01-15 18:42:21 -0500 )edit

Hey @macumber, Any suggestions please on volume calculation.

Karthick's avatar Karthick  ( 2018-12-18 21:49:05 -0500 )edit

OpenStudio has a pretty simple volume calculation. My thought was to try to refactor out a volume calculation method from EnergyPlus and use that directly rather than try to replicate the same algorithm in OpenStudio. However, that might be a ways off. In the meantime, you can directly set the zone volume in OpenStudio using ThermalZone::setVolume as a workaround.

macumber's avatar macumber  ( 2019-01-18 14:10:14 -0500 )edit

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Asked: 2018-01-10 20:15:15 -0500

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Last updated: Jan 15 '18