A HVAC humidistat is a device that is used to measure and control the humidity levels in a home or other indoor environment. It is typically used in conjunction with a heating, ventilation, and air conditioning (HVAC) system to maintain the desired humidity level. The humidistat works by measuring the relative humidity in the air and then adjusting the amount of moisture that is added or removed from the air to maintain the desired level. This is done by controlling the amount of air that is circulated through the HVAC system. The humidistat is a very important component of any HVAC system as it helps to maintain a comfortable and healthy environment. It also helps to reduce the amount of energy used by the HVAC system, as it helps to keep the air at the desired humidity level without having to run the system at full capacity. By using a humidistat, homeowners can ensure that their home is comfortable and healthy while also saving money on their energy bills.