Sometimes, your entire network of ducts is full of issues if your home is old or your duct system hasn’t been maintained.
It is best to replace all your ducts instead of attempting to repair them in this case.
When central air became the standard way to heat and cool homes, many old homes had ducts retrofitted. Contractors used different techniques to determine how many vents a home needed at the time. Your rooms might lack vents, affecting their ability to maintain a comfortable temperature. If your home has an addition that isn’t connected to the duct work, adding a vent or two and connecting the ducts to that part is a good idea when replacing your ducts. Your duct insulation’s R-value determines how resistant it is to temperature changes. A system with a higher R-value is better insulated. New ducts can usually be installed without tearing up ceilings and walls, unless your home has a flat roof. When you have ducts in place, the new ones can be ran where the old ones were. If you don’t have ducts, the spots that will see the most change are the closets and the attic, where the ductwork will be ran. A few holes will have to be cut in order to install vents and returns but that is very minor. When upgrading to central air, you’ve already decided to buy an air handler and an outdoor condenser. But what about if you’re replacing old ductwork and already have an air handler and condenser? Well, if those units are old, it’s a good time to get everything done at once. Replacing your ducts alone will improve your heating, cooling, and energy efficiency, but those improvements will be small if your other HVAC components are old and worn out.