Ground floor plane height

Hello,

I have been working on a building from the top down, my ground floor plane is going to end up below 0m as I have set my floor planes incorrectly. Is there anyway I can drag the rest of the building up or change the levels so my ground floor plan is 0m. Will it automatcially assume that part of the wall is below the ground if I don't change it?

 

ALSO

 

I have basement room to model do I just draw these below 0m so that hevacomp kow they are below ground or do I have to set this up manaually.

 

The purpose of this model is to get steady state heating and coologm loads.

 

Hope you can help!

 

J