Extension of the IFC4 schema for simulation applications

As part of the [BIM2SIM research project](https://www.researchgate.net/publication/354574261_BIM2SIM_-Development_of_semi-automated_methods_for_the_generation_of_simulation_models_using_Building_Information_Modeling) our research group has investigated the existance of relevant information for thermal building simulation and HVAC simulation in IFC. We compiled the information in two Excel spreadsheets based on the current official release IFC4 ADD2 TC1.

[Requirements_IFC_HVAC.xlsx](https://github.com/buildingSMART/IFC4.3.x-development/files/8581757/Requirements_IFC_HVAC.xlsx)
[Requirements_IFC_BPS.xlsx](https://github.com/buildingSMART/IFC4.3.x-development/files/8581758/Requirements_IFC_BPS.xlsx)

Since the IFC schema is extremely complex, it is quite possible in individual cases that we have overlooked existing information. If this is the case, we ask for your indulgence. At some points in the tables, reference was made to the final report of the project. This is currently not yet publicly available, but we will link it here as soon as possible.

We would like to share and discuss this information in view of the development of further IFC versions. We hope that the results can help IFC to become even more widely used in the field of building and HVAC simulations.

Start by reviewing Requirements_IFC_HVAC.xlsx and Requirements_IFC_BPS.xlsx against the official IFC4 ADD2 TC1 schema. Determine which simulation and HVAC requirements are not already represented, then use the project discussion to establish agreed schema extensions; the issue does not define a specific implementation or test target.

Written by the indexing model from the issue text.