According to the DB documentation, when loading whole building infiltration (for scheduled natural ventilation), EN 12831 is used. Which clauses of this standard is used. I pinpoint this to either Annex G or subclause 6.3.3.4 of EN 12831:2017. I am however not 100% certain.
Furthermore, to minimise the stack effect when using calculated natural ventilation, I prescribe the outdoor dry-bulb air temperature and ground temperature to be the same with the use of EMS. I also make diffuse and direct solar radiation 0. There still exists a temperature difference of +-1C in the CTF model. Is it possible to create an actuator for internal air temperature? The only other variable which I can think of which should be limited is material surface emissivity as I am not sure if the sky temperature in DB is calculated according to Section 5.1.2 - 5.1.3.