Heating and cooling efficiencies of a personal air thermoregulatory system are not only determined by the physics of energy conversion efficiency but also influenced by the interactions between human body and clothing microenvironment. It was found that for a wearable air ventilating system, sedentary position can lead to higher heating and cooling power than standing position. Also, leaning on the chair backrest during sitting can further improve the air cooling performance in hot condition compared with a non-leaning position. These improvements are mainly attributed to the change of clothing microclimate at chest and back areas, where cooling/heating air is directed. It was also found locations of air outlets in a wearable air ventilating system can affect the cooling/heating performance. With the improved understanding of the influence of human and design factors, the study provides a guideline for the design of personal air thermoregulatory systems used for different body positions.