The ENERGY STARÂ® Qualified Quiet Series Humidity Sensing fan provides a solution for areas that have sudden increases in humidity levels such as bathrooms. The integrated humidistat senses the humidity level of the room and turns the fan on until the humidity level is below the preset percentage. The Quiet Series Humidity Sensing ventilation fan operates at a low sound level and features a contoured grill that almost disappears into the ceiling. At the highest point the grill projects only 1/2" down from the ceiling. The electronically balanced centrifugal blower wheel assures maximum ventilation with minimum sound.