Do I need to have a Humidistat?
The newer air conditioning systems now use humidistat to provide better humidity control and these units should have a humidistat.
However, there is no easy answer to this question. Before the days of programmable thermostats, it was a method used to control the humidity when no one was occupying the space and temperature control was not the priority. This method wasn't always successful depending on a number of indoor and outdoor conditions but usually provided acceptable results.