Airnode Volumina Virtual Surface
The volume calculation in Trnsys3d requires a closed polyhedron. If the virtual surfaces aren’t defined correctly they won’t be written into the *.b18 during the first import. Therefore, the exported *.idf is missing virtual surfaces and the airnodes are no longer closed polyhedrons.
During the reimport into TRNBuild the volume is therefore calculated incorrectly. Virtual surfaces have to be defined as floor/ceiling and wall (not as roof), respectively.
Thus, it is recommended to check in the *.b18 file (using a text editor) if all virtual surfaces are present after the first import. If opening an exported *.idf in Sketchup you may also check if all virtual surfaces are there. If not, they have to be added there again.