A forced-air heating system has two duct systems. One provides the path for the conditioned air to go from the furnace to the rooms around the house, the second duct system allows the air in the rooms to return to the furnace for heating or cooling. These ducts are made of metal and can expand and contract from the temperature of the air. This movement in the ducts causes them to rub against the wood floor boards, causing creaking.
Turn off the home's televisions, radios, computers, dishwashers and anything else that makes noise.
Turn up the furnace's thermostat to activate it in the heating mode.
Walk around the house and listen closely for the source of the noises. The basement is the ideal location to identify squeaky ducts because this is where the majority of the duct work runs.
Push mineral wood in between the ducts and the floor sheathing where the squeaking is located. This provides a barrier between the metal and the wood, reducing the rubbing.