Most ductwork is installed in attics and crawl spaces where it isn’t thought about ever again. This can be detrimental to the effectiveness of the air conditioner.
If a central heating and air conditioning unit is the heart of home comfort, then the air ducts are like the arteries that carry the comfort throughout the home.
However, homeowners should stay away from 'DIY' channels and tutorials. It is not safe to work on a heater system without years of experience and the right tools.