You can use spaces and zones to aid in calculating the heating and cooling loads for a building plan.
After you create spaces and zones, you can assign to them engineering data necessary for calculating loads and airflows. You export the engineering and building information in Green Building XML (gbXML) format. You can use gbXML files in external analysis tools. After you analyze the file, you can import the results into your drawing. You can view the calculated loads and airflows for the spaces and zones, and design your duct systems accordingly.