You might be losing lots of air, leaking through your duct work resulting in an inefficient system and high electric bills. Normally your duct work will be in the basement. For houses with a second zone unit, the duct work will be in the attic.
For forced air systems in basement:
Inspect visible duct work, most air leakage will occur in the connections. An easy way to prevent this air from leaking is to wrap all connections with aluminum duct tape. Another way is to go over all connections with duct seal. This material is applied to duct connections with a brush. The material is soft when applied and will eventually harden and create a leak free duct connection. This second method might be more expensive but is likely worth the money. You will do this only once. Using the aluminum duct tape might require repeating every few years.
For forced air units in attics:
For this kind of ductwork you should repeat the same steps as in the basement to prevent air leaks and increase cooling and heating efficiency. However, attics are normally “non conditioned” space which means all ducts in that space need to be insulated. A non-insulated duct in an attic or a poorly insulated duct, constitute a SERIOUS source of lost energy as well as condensation.
Duct wrap should be used to insulate all ducts. In many cases, duct wrap will be dated. Inspect!!!
Summary:
Basement ductwork:
Seal all connections with aluminum duct tape or duct seal (apply with a brush).
Attic ductwork:
Seal all connections with aluminum duct tape or duct seal (apply with a brush).
Wrap or rewrap all ductwork with duct wrap.
