Spaces are entities that model the interior spaces of rooms and are grouped into zones. A zone represents an actual building zone that has its own heating and cooling requirements. Spaces and zones aid in calculating the heating and cooling loads for a building plan.
After you create spaces and zones, you can assign them the engineering data needed for calculating loads and airflows. You export the engineering and building information in Green Building XML (gbXML) format, that are used 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.