When describing a gas furnace modulating, the gas valve is constantly adjusting to allow more or less gas into your furnace to better regulate the heating in your home. All modulating furnaces come with a variable speed blower motor. Most brands use a timer to control this operation. When paired with the Carrier Infinity Control, your modulating furnace will regulate the output of your furnace to provide a constant air temperature in your home as required by the room temperature. The Infinity Control will also regulate the fan speed to provide a blanket of warm comfortable air circulating throughout your home and will all but eliminate hot and cold spots in your home.