Ducts are used to distribute conditioned air throughout houses with forced-airheating and cooling systems. Duct tubes are round or rectangular and are made of sheet metal, fiberglass, or other materials. Most homes have a duct system that delivers cooled or heated air from the air conditioning or heating unit to the home's living spaces.
According to Energy Star www.energystar.gov, in typical houses , about 20 percent of the air that moves through the duct system is lost due to leaks, holes, and poorly connected ducts. Leaks in your duct system may be caused by:

  • Ducts that are disconnected
  • Connections between ducts that are not properly sealed
  • Ducts that are sealed with poor quality materials
  • Small or big holes in ducts

Duct Sealing Benefits The result is an inefficient HVAC system, high utility bills, and difficulty keeping the house comfortable, no matter how the thermostat is set. Because ducts are often concealed in walls, ceilings, attics, and basements, repairing them can be difficult. What can you do to improving duct performance in your house ?
Start by sealing leaks using mastic sealant or metal (foil) tape and insulating all the ducts that you can access such as those in the attic, crawlspace, basement, or garage.
Never use 'duct tape' as it is not long-lasting. Make sure that the connections at vents and registers are well sealed where they meet the floors, walls, and ceiling. Note that duct sealing is not required for systems having less than 40 feet of ductwork in unconditioned spaces like attics, garages, crawlspaces, basements, or outside the building, or if the ducts were constructed, insulated, or sealed with asbestos.
How long will the air duct sealing material last? The sealing material has been found in rigorous testing to last over 10 years without failure. What are the estimated savings?

A series of government reports have shown that air duct sealing can lead to up to $850 in energy savings per year. Some homeowners have saved up to 40% on their energy bill.
Naturally, exact savings are difficult to precisely estimate since they depend on a multitude of variables such as your weather, house condition and design, your heating and air conditioning system , system usage - as well as other factors like energy prices.