Why a negative zone volume?
I have this very symmetrical building and EnergyPlus warnings as follows,
* Warning * Indicated Zone Volume <= 0.0 for Zone=THERMAL ZONE: 1ST FLOOR A * ~~~ * The calculated Zone Volume was=-188.78 * ~~~ * The simulation will continue with the Zone Volume set to 10.0 m3.
* Warning * Indicated Zone Volume <= 0.0 for Zone=THERMAL ZONE: 2ND FLOOR A * ~~~ * The calculated Zone Volume was=-188.78 * ~~~ * The simulation will continue with the Zone Volume set to 10.0 m3.
I can set the zone ceiling height to what I know it to be and the warnings go away. Leaving on auto calculate and I get negative volumes. Not a show stopper but just very curious as to what might be at play here.
Comments
woah that's super weird. There is an OpenStudio script in SketchUp that resets origins - try running that and see if you still get the error. Maybe also try deleting the zone floor and ceiling and then redrawing them. You shouldn't be getting negative zone volumes. In earlier versions of EPlus, this would have thrown an error - see this issue on Github.
Is there a way to check that the faces are being exported properly & that they are oriented correctly? If the faces are reversed in Sketchup, when the plugin writes the IDF file, it could be essentially pointing the faces the wrong way and resulting in an incorrect volume calculation you could check this my checking what the cardinal orientation of the faces are in the EnergyPlus output tables.
Is this in EnergyPlus 8.8.0?
Re @kwalkerman's comment, look specifically at the inside walls for zone 1a and 2a. Noticed they didn't match properly. That could mean they are just not aligned, or could mean one is reversed from expected face normal.
EnergyPlus 8.8 changed the zone volume calcs. From my initial experience, it seems like this new code catches more bad geometries, but can fail on complex geometries and it is difficult to understand why. In this particular case, it looks like you've found the issue.