As homes are being built tighter to save energy, effective ventilation is a must. Excessive humidity results in uncomfortable interiors, and provides an ideal environment for mould growth.
A recent article in Fine Homebuilding features a relatively new bathroom fan from Panasonic with sophisticated automatic controls.
WhisperSense fans have two levels of control: The default control is a motion sensor that activates the fan as soon as someone enters the bathroom. When the sensor detects that the person has left the bathroom, the fan continues to operate for an adjustable interval of time ranging from 1 to 60 minutes. The second level of control is triggered by a humidity sensor. After the interval of run-time initiated by the motion sensor winds down, the fan will stop—unless the humidity sensor detects that the relative humidity of the bathroom air is above the control’s humidity set point. If it is, the fan will operate until the room’s relative humidity drops to the set point (adjust-able from about 30% relative humidity to about 80%).
The trouble with humidity controls is that they need to be adjusted seasonally. During the winter, a bath fan may need to run for just a few minutes to bring the relative humidity down to 40%. During the summer, though, the same fan could run all day and never reach the set point—especially in a house without air-conditioning. As long as a homeowner understands this concept and is willing to fiddle with the settings every May and October, humidity control can be a useful feature.