Relative humidity plays a dominant role in determining thermal comfort for occupants. The existing ventilation performance metric associated with thermal comfort, namely the Effective Draft Temperature (EDT), fails to incorporate the influence of relative humidity on thermal comfort. This chapter introduces a novel ventilation performance indicator termed the Effective Moisture Temperature (EMT) to account for the combined effects of air temperature and relative humidity on thermal comfort. The proposed EMT is defined by establishing an analogy with the EDT framework, and its quantification is achieved through theoretical analyses of thermal neutrality principles, the thermal comfort zone boundaries, and the equivalent transfer mechanisms between relative humidity and air temperature. For practical applications, the EMTs are systematically tabulated under both cooling and heating, considering different thermal comfort requirements. The results derived from Monte Carlo simulation experiments and the ASHRAE Global Thermal Comfort Database II indicate that under low air movement conditions, the accuracy range of the original EDT is 23.8%–88.0%, whereas the proposed EMT demonstrates a significantly higher accuracy ranging from 98.6% to 99.5%. Furthermore, this chapter extends the framework by developing the Effective Draft and Moisture Temperature (EDMT) for elevated air movement conditions, integrating the EMT model with the cooling effect of air velocity. Under such enhanced air movement scenarios, the extended EDT exhibits an accuracy of 84.1%–95.5%, while the EDMT achieves an accuracy level of 96.7%–99.2%. These newly proposed indices, EMT and EDMT, contribute significantly to the design and optimization of thermally comfortable built environments.