ArchiCube is an easy-to-use software for thermal 3D calculations and visualization. Its kernel is used by KaLiBat for specialized 2D cases, and can be integrated in other softwares (contact : J. NOËL).
Samples of cases in usual buildings geometries :

The gridding is automatic (no user intervention), and makes it possible to limit the number of degree of freedom by placing nodes at the right place.
For the moment ArchiCube can be freely downloaded (software in french).