Sealing residential duct leaks is a typically inexpensive project, with a short payback. And the same is true of duct insulation, if the ducts are located outside the conditioned space.
Duct energy loss is often estimated at between 10% and 40% of the average energy bills, which amounts to about $100-$400 per year/home as shown in the table.
The table can also help you assess how much you can save by fixing problems in your duct system.
If the ducts are located within your living space, the losses are less severe and it may not be worthwhile to seal or to insulate your ducts. But if they run in an unconditioned space as in a garage, or an attic or an un-finished basement, the potential loss is much higher.
Small investments with a short payback
A one-gallon bucket of mastic and a roll of self-adhesive fiber tape may cost you, say, $50, and should be enough for most duct sealing jobs. Fiberglass duct insulation is also relatively inexpensive.
Even if you hire a contractor, typical duct sealing and insulation projects are relatively inexpensive and very cost-effective.
Bigger investments on Ducts
Replacing your existing ducts with a new system, or altering its design is a lot more expensive. And it may not be cost-effective, and the payback too long.
But if you are going to build a new home or make a big renovation, you should consider their design - and high-performance windows and high levels of air sealing and insulation all over your home’s walls, ceilings and floors.
These improvements create the conditions for a short and straight duct system (that should be located in the conditioned space of your house, instead of running in a garage, or attic) or even to replace central heating or cooling systems with ductless systems.