11/11/10

Conceptual Energy Analysis inside Revit (4 of ?)

CEA Workflow 04 - demo - mass floors - option 3

So the rose (or green) colored glasses are off.  I have found a chink in the armor of my Revit CEA knight.  One of the new features of the auto-magical Create Energy Model checkbox is this.  As soon as you create a mass and assign a mass floor, Revit CEA assumes you want to include it in the energy calculations. 

(If you don’t assign a mass floor, then it assumes the mass object is a shading object…something, like an adjacent building, that could cast shadows on your building.)

However, Revit CEA cannot create the analytical zones or surfaces if multiple masses overlap and are not joined.  So, checking the Create Energy Model automatically joins overlapping masses.  It is important to talk here about a couple of ways to create a unified mass from a few discrete masses.  First there is the Join Geometry tool.  Second there is the Cut Geometry tool.  The Join Geometry tool is what I first used and is what is used by CEA to automatically join overlapping masses (if the creator doesn’t join them before hitting finish mass).  When I tried to run an analysis I got the following error message:

image

What to do now?  I submitted a support request….and in the meantime I kept playing with it.  At first I was stumped.  I didn’t know what I did wrong.  So after some time zooming, panning and spinning the model, toggling the view between mass zones, mass surfaces and mass floors, I noticed something.  I could only see it in the mass zone view.  A small gap in the zoning surfaces was showing.

Join Error

I tried the other method for joining two solids.  That is the Cut Geometry tool which cuts one solid from another.  As soon as I hit finish mass, the zoning model changed and the gap was gone.  I was able to send it up to Green Building Studio without error.

Aaahhhh, the sweet, sweet taste of victory!

So when subscription support responded back to me I happily told them what I had discovered and what I had done to fix it (their suggestion was to review the modeling best practice tips found in the CEA help menu).

The one thing that really irked me?  I had to hunt around for the problem.  The program did not tell me there was a gap in my zoning model.  Also, unlike when exporting a gbXML file from a more developed model, there is not a gbXML browser option that allows me to see the zones and surfaces in a tree structure and review them one by one.  So if the default zoning materials had not been translucent, I might never have seen the gap!

I have since expressed this to Autodesk through their Feedback page here.

I will get back on track with my next post which will be on the Energy Settings dialog and all that it controls.

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