Maintaining clean ductwork in your home will increase both the overall energy efficiency of your heating and air conditioning systems, as well as your comfort.
With central air and forced air heating systems, air is constantly being circulated throughout your house. As dust and other debris build up they can lead to two things. The first is clogged ducts that impede the flow of warm air in the winter when you are trying to heat your home and cool air in the summer.
Duct cleaning removes this material so your heating and air conditioning units don't need to work harder than normal in order to achieve and maintain target temperatures. This can cause damage to the overall system, requiring costly repairs and inconvenience. Not to mention the fact that you will be waiting longer while your home is heating up or cooling down if the ducts are clogged and dirty.
The second thing duct cleaning does is prevent the spread of allergens throughout the house. If you or anyone else in your home has allergies, specifically to dust and dander, a build-up of these allergens in the ducts of forced air systems will cause them to be repeatedly circulated in the air of your home. This can be especially bad for children or elderly residents.
Also, if you live in a climate with high humidity/moisture content, that moisture can build up inside ductwork and lead to mold. This can be blown through the system into each room of your house and be hazardous to your health. More and more people are realizing that household mold is a serious thing to keep an eye on. It can lead to respiratory diseases and other medical complications. Duct cleaning is one way to eliminate that hazard.
If you vacuum the house and dust the vents in each room regularly you can pick up much of the dust and dander that would be sucked up and circulated throughout the system. This will cut down on the potential build-up so that duct cleaning doesn't have to be done as often.
Make sure that you have high quality filters installed in your furnace and central air condenser, and have them checked periodically. And have the ductwork in the house professionally cleaned at least once every two years. People who have strong allergies or live in humid climates should consider duct cleaning once every year.
When cleaning your ductwork and heating/cooling system, be sure to service the entire system and not just the ductwork. Are the surfaces of the blower, heat exchanger, coils, fans, plenums, registers, grilles and diffusers visibly clean and free of debris? Are all access panels in the ductwork properly sealed? This means no duct tape, even though the name makes you think it would be appropriate. You want a permanent sealant for the job, not some form of tape that will lose adhesive properties after a while. These panels should be screwed securely into the sheet metal and then sealed with a mastic sealant. Are the drain pans cleaned and working properly? And are there any visible moisture stains or areas where mold might become a problem? You should see cost savings as well as extend the life of your furnace and air conditioning system by keeping the system and your ductwork clean.