  The designer's preoccupation to reduce the energy needs and get a better
thermal quality of ambiances helped in the development of several packages
simulating the dynamic behaviour of buildings. This paper shows the adaptation
of a method of thermal analysis, the nodal analysis, linked to the case of
building's thermal behaviour. We take successively an interest in the case of
conduction into a wall, in the coupling with superficial exchanges and finally
in the constitution of thermal state models of the building. Big variations
existing from one building to another, it's necessary to build the thermal
model from the building description. This article shows the chosen method in
the case of our thermal simulation program for buildings, CODYRUN
