I beg a pardon for so many questions, but OS is really not so obviously connected to E+ as it could be... The question is in the topic, simulation returns the same fatal error FindTDDPipe: Surface=SUB SURFACE 11, TDD:Dome object does not reference a valid Diffuser object....needs DaylightingDevice:Tubular of same name as Surface. In E+ TDD object looks different and has additional settings to model it. Does OS support TDD the same way?