The cost of a new residential HVAC system is significant enough that many consumers opt to keep their existing ductwork and have a contractor make the necessary adjustments to retrofit the new system to the old ductwork. That raises a number of issues that any homeowner should consider before replacing the HVAC system.
Why keep the existing ductwork. Cost is the main reason not to replace the ductwork when you get a new system. Most HVAC contractors recommend against this, pointing out that it doesn’t make sense to pay for a new system that is more energy efficient and then use old ductwork that will certainly lower that efficiency rating.
No ducts in the attic. One reason to replace your existing ductwork system is that some or all of it is located in the attic. Because of the significant temperature swings in the attic, maintaining the temperature of air being pumped through the ductwork is much more difficult. Many experts say the purchase of a new HVAC system is the perfect occasion to remove those vents from the attic. Studies show that relocating ductwork out of the attic can increase the efficiency of an HVAC system by 25 to 30 percent. Attics can reach 130 degrees or higher in the summer. Imagine the impact on air traveling through vents in that temperature.
Mismatched systems are inefficient. If your HVAC system is 15 to 20 years old, a new system could be between 10 percent and 40 percent more efficient, depending on the specific efficiency rating of the system you purchase. If the air handler and other elements of the HVAC system were specifically created to match the ductwork in your home, it’s impossible for the efficiency not to suffer in a retrofit situation. Additionally, the lifespan of the new system is likely to be affected because of mismatched ductwork. Finally, even sealed ductwork systems begin to allow dirt and dust over time, which can significantly reduce the performance of the unit.
Ductless systems save money. The best answer could be a ductless HVAC unit. These systems are 20 to 30 percent more expensive than traditional units with ductwork. However, removing the ducts eliminates a major source of inefficiency, as leaks and cracks in the ductwork commonly develop over time Another option is a mini-duct system that relies on ductwork that is less than half the size of a traditional duct system. The mini-ducts work under higher pressure, which allows the system to be more efficient and save 20 to 30 percent on the monthly utility bills.