In our formulation of zonal models for calculating room air temperature and flow distributions, the behavior of a room is represented by the connection of SPARK calculation modules. Modules to describe the building walls and various systems have been created. They form the models library. By assembling the appropriate modules, a zonal model of an entire building can be constructed. A model-generating tool called GenSPARK automates this process. SPARK solves the set of equations resulting from this construction to obtain the air flow and temperature distribution in the building. We describe our formulation of zonal models, show how GenSPARK works and give examples of configurations we are able to analyze.