Ducts are an essential part of a forced-air system. The duct system used in air heating and air cooling your home is a compilation of tubes that distributes the heated or cooled air to the different rooms. They are commonly cloaked in walls, attics, basements, ceilings or crawl spaces. The duct system can have an important effect on the health of the occupants through the distribution of indoor air pollution.

Ducts that perform poorly may cause your heating and cooling system to work harder to keep your home at a comfortable temperature. Any changes or repairs to your duct system should always be performed by a qualified professional.

Some conditions that can be a sign of poorly performing ducts:

• High utility bills in the summer and winter
• Your system's filters get dirty quickly
• Rooms are stuffy/don't feel comfortable
• Your ducts are not insulated or the insulation is damaged
• Flexible ducts have kinks in them or are tangled

Some tell-tale signs of problem ducts:

• Uninsulated ducts in unconditioned spaces
• Disconnected,torn,damaged ducts
• Blin-alley ducts (they lead nowhere)
• Inadequate return-side duct work
• Evidence of supply-and-return-side leakage

A well designed and properly sealed duct system can make your home more comfortable and more energy efficient.

The duct system is usually located within the walls, floors and ceilings. Typically, you can only see the outlet, which is a register enclosed with grillwork.

The system consists of supply ducts and return ducts. Central heating or cooling equipment includes a fan that forces heated or cooled air into supply ducts leading to the rooms. The fan gets air supply through return ducts. To save on installation costs, the majority of homes have one or two return registers located in common areas (i.e. hallways).

Typical duct systems lose 25% to 40% of the heating and cooling energy put out by the central furnace, heat pump or air conditioner.

Duct systems can lose energy in one of two ways:

1. Conduction
2. Air Leaks

Conduction

One way to lose energy is for the warm air inside the ducts to heat the duct walls, which in turn heat the cold air outside the ducts. If the ducts are in the attic or crawl space that is nearly as cold as the outdoors, this heat is entirely lost. If they are in the basement, some of the heat lost from the ducts may be recaptured by warming the basement ceiling enough to decrease the heat lost from the home. The same information applies to cooling when the air conditioner is on.

Air Leaks

Another way to lose energy is through air leakage. There may be leakage from accidental holes in the ducts or duct sections that are poorly connected. Leakage from the duct system can be hazardous to your health. If the return duct leaks, their low pressure can pull down the pressure in the basement/garage also. This can suck flue gases from the furnace and radon gas from the soil around your home. The flue gases, if containing carbon monoxide, can be hazardous. Radon gas exposure is the second leading cause of lung cancer after smoking. Upgrading the energy efficiency of the duct system may help avoid these potential problems.

When a qualified professional repairs your duct system, it is likely that the quality of your indoor air will improve. A qualified practitioner will perform the necessary tests to ensure that no problems are created where they did not exist before.

If you choose to have your ducts cleaned, the service provider should:

• Open access ports/doors to let the wholesystem to be cleaned and inspected.
• Inspect the system prior to cleaning to ensure that ther eare no asbestos-containing materials in the heating and cooling system.
• Use vacuum equipment that exhausts particles outside of the home or use only high-efficiency partile air (HEPA) vacuuming equipment if the vacuum exhausts inside the home.
• Protect carpet and furnishings during cleaning.
• Use well-controlled brushing of duct surfaces along with contact vacuum cleaning to remove dust as well as other particles.
• Use only soft-bristled brushed for fiberglass duct board and sheet metal ducts lined with firberglass.
• Protect the duct work, including sealing and reinsulating any access holes the service provider may have made or used so that they are airtight.