# Modeling plenums in Openstudio

I've observed how plenums are added in the HVAC systems tab for OS. In my model though, I'm having problems with intersection and surface matching when actually adding plenums to the geometry: there are mis-assigned surface(s), some are lost, and sometimes new problem(s) arise when I re-open the file. Any suggestions on ways/systematic approaches to minimize or eliminate surface intersection and matching problems? I'm careful with making nice orthogonal lines and using the Create Spaces option or New Space before drawing new spaces. Any alternate approaches on plenums, i.e. setting adjacencies properly if not including the plenum geometry in the model?

@Suley. retag 'plunums' to 'plenums' to get this sorted correctly.