QUESTION:

The south wall and the window should be exposed to the sun and outside temperature but the other 5 walls/roof/floor should not take part of the simulation. I want the temperature on the other side of this walls to be the same as in the room I want to simulate. I also plan to have a constant airflow with a constant temperature into the room.

ANSWER:

1. Make all the walls and ceilings (other than the south side) Partition objects. These are special in that they are assumed to be completely internal and do not conduct heat or collect solar radiation, but still add mass to the space. This is exactly what a wall between zones of equal temperature would do.
2. The only problem you do have is the floor. If you assign that as a partition you will not have any floor area in your space. Two things you can do here;
   1. assign the floor as a Partition object after the inter-zonal adjacency calc.
   2. or, create a floor material with a U-value, admittance, lag, decrement and solar absorption of 0 (or very very close to 0)