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# What is length and what is width? Along what axis?

In EP documentation there are many references to "Length" and "Width" of a surface. For example, "Floor:Adiabatic" is defined by one corner and the length and the width. What axis do we measure the length on and what axis the width? I could not find this mapping anywhere in the EP documentation. Does anyone have a clue?

For example, referring to the following coordinate system, if I am defining a Floor:Adiabatic object wityh the lower left corner coinciding with the global origin, what do I specify for L and W? A and B, respectively? Or vice versa?

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An alternative to OpenStudio (application and SketchUp plug-in) that reads and writes OSM files that eventually are translated to IDF files is Euclid, another SketchUp plug-in formerly known as Legacy OpenStudio that reads and writes to IDF files directly. Using Euclid, you can:

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I was not aware of Euclid. As you can see, I am new to the EP domain and my interests in using EP are probably different from the majority and I am still exploring the EP ecology. I looked up Euclid. I like that it is open source. I will try and learn more about it. Thank you for the mention.

( 2021-11-18 18:19:42 -0600 )edit

I had to dig into the source code to find the answer. For all objects in this list:

"Wall:Exterior",
"Wall:Interzone",
"Wall:Underground",
"Roof",
"Ceiling:Interzone",
"Floor:GroundContact",
"Floor:Interzone"


you will find a similar structure, where you have these fields in this order:

X
Y
Z
Dimension1 along X' (=Length in MakeRectangularVertices)
Dimension2 along Y' (=Height in MakeRectangularVertices)


See here, how these are passed to MakeRectangularVertices: https://github.com/NREL/EnergyPlus/bl...

So in your case, for Floor:Adiabatic, Length=Dimension1, Width=Dimension2. So the Length is A and the Width is B on your image.

Side Note I would advise to refrain from using these objects, instead use a Building:Surface:Detailed. Draw your geometry in a tool such as the openstudio-sketchup-plugin or Euclid. That way it's clear what you are actually drawing.

In you insist, I suggest doing QA/QC, by making use of the Output:Surfaces:Drawing object, like so: Output:Surfaces:Drawing, DXF;. You could also try to import your IDF in a tool that would visualize it directly (such as the OpenStudioApplication, via File > Import > IDF)

Disclaimer: I am a contributor to the OpenStudioApplication and openstudio-sketchup-plugin

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Very clear and informative answer. Much appreciated. Thank you verty much.

( 2021-11-18 18:14:31 -0600 )edit

Sure thing, and welcome to Unmethours!

If you allow me to be pedantic (as people are on a similar site like Stack Exchange), I find it interesting that you marked the other answer as accepted as it doesn't actually answer the original question (which is about length and width).

(Also, Aaron and I both omitted the usual disclaimers: his company, Big Ladder Software, develops Euclid, and I am a contributor to the OpenStudio suite of tools (which is also free open source software). I edited my answer to add the disclaimer and Euclid as an alternative tool)

( 2021-11-19 02:21:50 -0600 )edit