Notes that ultrasonic humidification has become increasingly popular for both indoor air quality and energy related reasons. Presents a thermodynamic comparison of steam and ultrasonic humidification. Stresses a number of design and operational issues connected with ultrasonic humidification, in particular heating coil requirements, supply air temperature control sensor placement and the impact of the size and number of stages of humidification on supply air temperature control hunting. Finally, develops the analytical tools, currently missing from both private and large public domain energy analysis software, and applies them to a specific academic library building.Units: DualKEYWORDS: year 1997, Humidifying, humidifiers, ultrasonics, indoor, air quality, computer programs, designing, libraries, USA, sensors, supply air, comparing, steam humidifiers