How is the termal behaviour of the ground near the building depending on
the ambient temperature and the temperature within the building?
We have two new 3-d conduction models of the ground available for TRNSYS; 
one for interaction with slab floors and one for interaction with 
basements.  The slab floor model also has the option of running pipes 
through the slab and/or soil for radiant heating or thermal storage 
applications.  Both of these models can interact with the multi-zone 
building model in TRNSYS (Type 56) and with the ambient.  Let me know if 
you'd like me to send you some more detailed information.