HVAC- Heating, Ventilation and Air Conditioning.

HVAC- Heating, Ventilation and Air Conditioning.


The duct, or air distribution system used in cooling and heating your home is a collection of tubes that distributes the heated or cooled air to all the rooms in the house or building. This branching network of tubes usually constructed of sheet metal, fiberglass board, or a flexible plastic-and-wire composite is found within your home.

The duct system is designed to supply all the rooms with air, that is “conditioned” (heated or cooled by the heating, ventilation, and air conditioning (HVAC) equipment) and to circulate or return the same volume of air back to the HVAC equipment.

Typical air-duct systems lose 25 to 40% of the heating or cooling energy put out by the cooling and heating system.

One way in which conditioned air is lost in the duct system is leaks, these make the HVAC system work harder, thus increasing your utility bill. In addition, duct leakage can lessen comfort and endanger your health and safety ( this is very important to know).

Your duct system has two main air-transfer systems which are supply and return. The supply side delivers the conditioned air to the home through individual room registers) what you feel blowing out of the registers, the return side withdraws inside air and delivers it to the air handler of your central system. All of the air drawn into the return duct(s) is conditioned and should be delivered back through the supply registers.

The following figure will show you areas where there are problems with the ducts and vents



Where Do You Look For Leaks?

Major leaks can be found around joints at ductwork connections, near vents, around the air handler unit. Look for holes, tears, and loose joints. Every unsealed joint will likely have a small leak, even if a gap is not visible. Make sure registers and vents are firmly attached. If your home has a mechanical closet, it should also be properly sealed to prevent negative return-side air leakage. The return chamber should be kept free of debris at all times.


What Is the Best Way to Seal the Leaks?

It is always best to have a licensed HVAC (Heating, Ventilation and Air Conditioning) contractor repair your system’s duct leaks. Return duct leaks are difficult to detect because the larger return ducts operate at a lower air pressure, and air is being drawn into the system. And if you only repair the supply duct leaks, even more unconditioned air may be drawn into the system. Supply-duct leaks are more easily noticed because you can feel air blowing out from the connections or see nearby insulation moving.

Duct leaks can be sealed using mastic or acrylic-adhesive foil tape. Mastic adheres well to most surfaces and provides an effective long-term seal. Mastic alone may be used to seal cracks less than ¼” wide. Foil tape carries a 20-year guarantee if applied properly.

Any sealant should carry the Underwriters Laboratories rating (UL-181) specific for that particular type of duct. Most duct manufacturers now list the closure products that they allow to be used with their ducts.

If you see the contractor bringing in duct tape, make certain they do not intend to use it on ducts. If they do, then hire someone else. In the past, many systems were sealed with a gray, rubber-adhesive, cloth-duct tape. This tape will eventually disintegrate due to its short-lived rubber-based glue. If you see this kind of tape in an existing home, be sure to check all areas where it is attached to the ductwork. If your contractor insists on using duct tape on the ductwork, use a different contractor.