I have always been very conscientious about replacing the air filters in the furnace and air conditioner every month.
I schedule professional maintenance for the heater in the fall and the cooling system in the spring.
I am not sure why I forgot about taking care of the ductwork. I think that because the pipes are hidden in the walls and ceiling, I just never considered the need for service. I was not happy when my furnace had trouble keeping the house warm last winter. The heating system seemed to be running non stop and yet the temperature was inconsistent from one room to another. No matter how high I adjusted the thermostat, the house felt chilly. The furnace is not that old and should have been able to handle the cold weather. I also noticed that there seemed to be a lot of dust floating around, and my monthly energy bills were higher than normal. I finally hired an HVAC contractor to check out my furnace. The technician inspected the heating system and found that the problem was caused by the ductwork. There was a considerable buildup of contaminants in the pipes. The accumulation of dust, pet dander, pollen, mold growth and even dead rodents was blocking airflow through the pipes. Because the maximum amount of air was failing to reach the various rooms, it was forcing the furnace to run more often, work harder and use more energy. There was greater wear and tear on the heating system. The technician provided a duct cleaning service using equipment that looked a lot like an industrial vacuum cleaner.