Where should I set my humidistat?

Every house is different. Just as your windows, doors and amount of insulation in your home affects your home's energy efficiency, it also determines where to set your humidistat. You will need to experiment to find your home's best humidistat setting; but remember, it can take a few days for the house to show changes in the humidistat setting.

If you notice condensation on your windows, you will need to turn your humidistat down.

"Lets say that the outdoor temperature is 0 degrees C, or 32 degrees F. The maximum amount of water that a cubic meter of air can hold at this temperature is 5 grams. Now you bring this cubic meter of air inside and heat it to 25 degrees C or 77 degrees F. The relative humidity is only 23 percent:
5 grams of water in the air / 22 grams possible = 23 percent relative humidity"
          --How Stuff Works

Did you know? Some humidistats display a temperature guide. It is important to remember that this is only a guildeline. Its main purpose is to guide you that as the temperature drops outside, so should your humidistat setting.

I have a barometer in my house and my humidistat is not accurate.

Two (2) important points to remember:

Most humidistat sensors are mounted in the ductwork and can only read the humidity of the air that is passing it.

Many household barometers, when tested with a sling psychrometer (a device to test humidity), are not accurate.