There is usually discrepancy between deterministic modeling and actual operations of HVAC (heating, ventilation and air-conditioning) systems to some extent depending on the model comprehensiveness. Our main challenge is to express associated uncertainty in model outcomes in a way that is helpful to those trying to use the predictions from simulations to make decisions. Considerable research is underway to quantify uncertainty in building simulation. A recent trend is to include HVAC system parameters in uncertainty analysis. Outdoor air control has significant impact on energy consumption and indoor air quality. This study investigates the uncertainties of outdoor air control of a particular system type. Based on the analysis, the authors have identified the uncertain parameters, quantified their uncertainty patterns and mapped them to building performance simulation in terms of energy consumption and ventilation requirement. The simulated results show that the uncertainty in outdoor air control can lead to 17% difference in cooling consumption and 43% difference in heating consumption compared with using standard outdoor air control settings in EnergyPlus simulation. The effects of the identified uncertainty on fault detection are also discussed. (C) 2016 Elsevier B.V. All rights reserved.