The HVAC systems serving the Operating Rooms could not maintain acceptable levels of humidity during both heating and cooling seasons. To raise the humidity in the heating season, new humidifiers were selected for each AHU serving the Operating Rooms. Each humidifier was selected with modulating capability for tighter control and with short absorption-length, duct-dispersion grid tubes. To better control humidity in the summer, a booster chiller system was installed. The new system required primary and secondary pumps, a buffer tank to add chiller side water capacity, a glycol feeder tank, a plate heat exchanger (to isolate the glycol water from the building water side), piping changes and a custom sequence design for the controls.