I would like to model a room completely located under ground. As a start I builded a simple room without windows and place it 1m under the ground level. In order to validate that the ground temperature was used rather than the outside temperature for the walls, floor and ceiling I set all other gains to 0 and would expect the room temperature to be around the ground temperature, however this is not the case, the programm clearly used outside temperatures.
My questions are:

1) How can I make sure a wall is adjacent to the ground and uses the ground temperature.
2) Can I set a user defined ground temperature.

/Br Rob