Energy Analysis Fails using Detailed Elements?

[Anonymous]

I have attached a Revit model and corresponding gbXML that I am trying to analyze, using the "Detailed Elements" option selected.  However, GBS seems to analyze it up to about 20-30% and then fails.  I am able to complete analysis using both conceptual types and schematic types.

[mstein7484]

Hi Neil,

When selecting "Detailed Elements" for the analysis the Detailed set of constructions specified in your model are used (as compared to the Analytical  Construction Types found, or the Conceptual Constructions found in the Energy Settings dialog).  DOE2 (the simulation engine used by GBS/Insight) has limitations with the thermal properties of constructions when the layers have very high or very low thermal mass. The Analysis Failed email from the Insight services includes an error message, which references the layer with the problem. You can search the gbXML file to find which construction uses the layer with the problem. In this case it's the Compound Ceiling Plain construction with problems. In terms of the energy simulation the steel stud is defined as solid sheet of steel and is seen as DOE2 as a construction with a very low thermal mass. By switching the ceiling construction to Generic Ceiling the simulation works.

Let us know if you have more questions on this topic, otherwise please accept as a solution so that others can benefit from this information.

Regards,

[Anonymous]

Thanks for you help.  I have replaced the ceiling as suggested, however I am still getting analysis failure.  I've attached the files.

[mstein7484 · Accepted solution]

Hi Neil,

This time it's the same problem, but with the "Stud Wall." If you encounter similar problems again, you can investigate which construction causes the "too thick/too thin" error by searching the xml file for the layer referenced in the error message. Again, these errors are from DOE2 limitations when trying to simulate combined layers of materials with very high or very low mass. Try removing the metal stud material and/or replace it with an air layer. This change will make virtually no difference with the energy results.

Let us know if you have more questions on this topic, otherwise please accept as a solution so that others can benefit from this information.

Regards,

[Anonymous]

Got it sorted.  Did what you said about changing the metal internal walls.

How do I check the gbxml to see what is causing the problem?

All I got was:

[mstein7484]

I followed the first bullet-point tip & looked at the error found when mousing over the failed run in GBS. It references the layer id with the "too thick/too thin" error.

Regards,