A new computer simulation tool, named “CHAMPS-Multizone” is developed for analyzing the performance of both building energy and indoor air quality. The simulation model includes the dynamic effects of outdoor climates, building materials and envelope system, air flows in multi-zones, internal heat and pollutant sources, and operation of the building HVAC systems. The governing equations, adopted assumptions and preliminary validation and case simulation results are discussed in this presentation. The needs and challenges for further development are also discussed. To model CHAMPS-Multizone simulation program in a structure way, a Building Information Modeling (BIM) method (called “Virtual Building”) is introduced. The method is not only implemented in CHAMPS-Multizone program for simulation purposes but also used for whole building performance monitoring. The system structure, data transfer modules, and sensor network used in virtual building network are discussed for monitoring purposes. The Virtual Building system is used to monitor a LEED Platinum building in central NY climate condition. Preliminary monitoring results are presented regarding the case building’s indoor environments and energy systems.