Many homes have an additional control device next to their Heating plus Air Conditioning thermostat that regulates the whole system based on indoor humidity levels. This control component is properly called a humidistat plus can have one of multiple primary functions depending on your weather conditions. If you live in the north, a humidistat is officially installed to control the humidifier connected to the Heating plus Air Conditioning system. You then set the humidistat to a particular humidity level between 0 plus 100%, and it will turn on the humidifier when the humidity levels drop below the value the control is set to be at. This is to offset the extreme dryness in Winter conditions and indoor heat. On the flip side, if you live in warmer yet wetter weather conditions, as in the south, your humidistat is officially installed to tell the thermostat when to turn on the air conditioner. If you only have a thermostat, your air conditioner is only told when to run based on temperature levels alone. You set it to 76 degrees, then the air conditioner knows to run as much as necessary to keep the indoor temperature at that level. However, if you add a humidistat to the mix, you can now bypass the thermostat based on the humidity levels. Let’s say you want to leave for a month, but you don’t want to turn off the AC because of mold concerns. If you set the humidistat to 60%, it will bypass the thermostat, where it will only allow the AC to turn on when humidity levels inside rise above 60%. This way, if it’s dry outside in the middle of the day, when moisture levels are their lowest, your AC won’t keep kicking on to maintain the temperature. It will then only turn on when needed to keep the humidity inside down to a respectable degree. Unfortunately, periodically humidistats can be off by 10-20%, so it’s best to test them with humidity meters to see if your system is laboring accordingly. If you’re living in a frigid environment, too much excess humidity from your humidifier can create condensation on walls plus windows, so it’s best to always consider this factor plus monitor it closely.