Energy consumption of the office buildings demonstrates potential energy savings. One of the major parts of the energy consumption in these building is related to the heating, ventilation and air conditioning systems which keep thermal conditions in a comfort zone and indoor air quality in an acceptable range. Nowadays, building management systems are developed to reduce the energy consumption of these systems besides supplying occupants with comfort conditions. Furthermore, these complex systems can be faced by different operation faults. To diagnose and detect these faults, getting the knowledge about the system behavior through modeling is substantial. This paper introduces a scalable multi-zone office building model that was established in Matlab/Simulink using Simscape toolbox. The model contains the thermal dynamics of the building elements and the heating control system which is equipped with demand-controlled ventilation. The results show that the model can correctly describe and predict the dynamics of the system. The proposed approach is intended to be used for HVAC systems in building automation with a specific focus on faults diagnosis and detection.