Occupancy information in a building is critical in terms of indoor environmental quality, energy consumption and building energy simulation. However, it is not easy to gather and model the occupancy information. Within the framework of institutional buildings, the large occupancy number and the very high occupancy variation will pose a higher challenging for occupancy number counting and modeling. This review paper reviewed the techniques and modeling methodologies in buildings and listed the pros and cons for further consideration for the application in institutional buildings. (C) 2015 Elsevier B.V. All rights reserved.