According to Energy Star In a typical house with ducting about 20 to 30 percent of the air that moves through the duct system is lost due to leaks, holes, and poorly connected ducts. The result is higher utility bills and difficulty keeping the house comfortable, no matter how the thermostat is set.
Poorly designed, older, dirty duct systems can cause equipment failures, higher energy bills, higher contaminants in the home, and many other issues.
Bottom line don't over look your duct system when replacing your heating and a/c equipment.
If your duct system is 15 years old or older it is likely in need of replacement. Having a properly sized, designed, sealed, and installed duct system will more than pay for itself over its lifespan.
