A refrigerator includes a storage compartment and a mullion assembly pivotally coupled to one of a first door and a second door. The mullion assembly includes a cavity with an insulating member disposed therein. One or more sensor assemblies are coupled to the mullion assembly and configured to collect data sufficient to calculate a dew point temperature of the mullion assembly and an actual temperature of the mullion assembly. A heating element is coupled to the mullion assembly and is selectively activated by a controller based on information provided from the one or more sensor assemblies. The heating element is powered using a modulated power level that is inversely proportionate to the difference in temperature between the mullion assembly and the calculated dew point.