You can export the current building model in gbXML format using the Export gbXML model command from the File > Export menu. This opens the gbXML Export dialog. Press OK to confirm and select the name of the gbXML file to be created.
The gbXML file includes full surface geometry, zone lists with names, windows, doors, shading devices, constructions, materials and glazing systems. Note that all other data is not exported. So no data is stored on activity, lighting, HVAC and model settings.
gbXML files exported from DesignBuilder can be imported into any other software supporting the gbXML standard file format, including DesignBuilder v3 and later.
Tip: It is not generally possible to load models saved in DesignBuilder format into earlier versions, but as an alternative you can export gbXML from a recent version and import that into earlier versions of DesignBuilder supporting the gbXML import.