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Re: [EnergyPlus_Support] IFC to IDF, Geometry, Relative coordinates

At 05:16 AM 11/29/2002, Monjur M Mourshed wrote:

a.       Walls are not connected but have an offset of 0.19m (Half the width of the Wall ? 0.38 m).


                  Will that be a problem in E+ simulations, if walls are not connected? There?s a gap of 0.19m between walls and floor/ roof. My understanding is that, EnergyPlus is not like nodal simulation (like CFD), so it probably takes in only Area and Volume to calculate. In this case it does not matter if the walls/ slabs are not connected to each other. Am I right?

It should not be a problem for EnergyPlus.  It might be....if you specify Solar Distribution as FullInteriorAndExterior, but I'm not sure about that.

NOTE: I tried to define zone in different ways (ArchiCAD has 3 ways to define a zone) ? Every procedure gives me the same result.


b.       If you take a closer look at figure 2 (bit rotated in AutoCAD to view the triangulation), you will see that both the slabs (floor/ roof) are triangulated instead of rectangular profile.


Is that a glitch in BSPro/ IFCtoIDF? Just curious. Did anybody face similar problem?


I don't know the answer to that one.  I'd suggest looking in the IFCtoIDF manual to see if it is covered there.  That is, it may not be a glitch but rather a feature -- to triangulate all "flat" surfacs would allow for non-rectangular zones to be handled the way EnergyPlus might need them automatically but will make things a bit strange for the simple, rectangular zones.

(You could try making an L-shaped zone and see if the floor comes out looking reasonably correct and goes into EnergyPlus correctly).


Figure 02: Rotated using 3D Orbit in SW Isometric view. Note the traingulation


NOTE: I guess, BSPro took wall centreline (cL) as the wall plane. But zones are created from inside dimensions of the wall.

There may be an option in Archicad and/or the app that reads the IFC file that would change this interpretation of centerline vs. inside dimension vs. outside dimenion use?


I have corrected the coordinates (vertices) manually so that it looks like figure 03. Well, changing tens of coordinates for this file was tiresome but possible. What if ? I have a big building, consisting of a number of zones and hundreds and thousands of vertices?

Will I have any trouble if I use the IDF file (figure 01, 02 - without any editing) and use it in simulation/ Do I have to edit the vertices so that they are connected?

As I said above, you really should have no problem. 


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