Leaky ducts can cut into air-conditioning efficiency. Ductwork must be balanced between the supply and return sides of the system in order for it to work safely and efficiently, so making a repair in one section can cause a problem in another. Leak-prone areas include the return plenum; where branch ducts meet the trunk line; and where ducts attach to outlets. Also, insulate ducts that run through a hot attic with a blanket of R-11 fiberglass insulation.
Unless the duct repairs are minor, it's wise to leave them to a HVAC pro. While the contractor is on site checking your ducts, have him tune up the air-conditioning unit by cleaning filters, unplugging coils, unblocking drains and lubing the fan.
Cost: $75 to start for a service call
Benefit: Up to 40 percent off your cooling bill