In thermal building applications, simplified physical models are commonly used by engineers. In multizone models, a building is decomposed into zones and envelopes. As the temperature is assumed homogeneous in the zones, the time evolution of the zone temperature is described by an ordinary differential equation. Concerning the envelopes, a one-dimensional partial differential equation is considered. This simplifed physical model allows to simulate at a reasonable computation cost the thermal behavior of the building. It is particularly useful to evaluate the energy effciency of the building and to propose an optimal control of the building systems such as the heating and the ventilation.