To develop a thermal model you will first have to create a building model by inputting and zoning the geometry in the 3D Modeller. This is the geometry input phase.
This stage is easy achieved by tracing round 2D architectural CAD drawings, although Tas also offers interoperability with building information modelling (BIM) through its capability to import files created under the gbXML schema.
With the geometry in place you are now able to use the software to "interact" with the building geometry, either for client presentations or troubleshooting any errors and warnings that may have crept in. A number of options are available to you. You will be able to display shadows and select different viewing angles. You will also be able to use the View Setup dialog (more about this later) to simulate walking/moving around inside and outside the building. You can perform operations like zoom, pan, orbit, and rotate by using the tools available on the workspace, and you will be able to turn floor levels on and off and do the same for different surface types. This is useful when you want to turn off surfaces such as a ceiling or roof to afford yourself with unobstructed views of different sections of the building.
When the geometry has been saved the file will be known as a "T3D", e.g. <filename>.t3d. Once you've completely drawn in the geometry the data for the same can be exported to the Building Simulator. The export process will produce a TBD file, known as a building data file. This is the stage at which you will start to provide a bit more information about the thermal model by adding construction data, weather, internal gains, control functions, and specifying the plant operation. For example, you will start by adding the weather data and then add details concerning the different constructions and gains, heating and cooling setpoints and when the building is expected to be occupied. Knowing the occupancy density will allow you to inform the model of the Watts per square metre you can expect to be emitted into the space at different times as a result of people's metabolic rate. You can also enter the expected heat gains that will be produced by running equipment and lighting, as well as specifying infiltration and ventilation rates. If you've got a template set up and you use the Building Initialisation Wizard then the software will be able to save you a lot of time because it will add the building data to the model for you.
You will now be able to simulate the building data by running the calculation engine. Doing so will produce a simulation data file (TSD) which will automatically open in the Results Viewer. In your project directory you will now have your CAD drawings and all the core Tas files, including a T3D, TBD, and TSD.