Methods of Filling Spare Ducts

Return Ducts

• The return ducts provide a path for the building's air back to the furnace. These ducts are typically the larger rectangular registers found at the top or bottom of the interior walls. A single return duct services several supply registers and shouldn't be filled. The reason is that it causes the furnace fan to work harder in drawing air back to the furnace, slowing the speed of air movement over its heat exchanger and reducing the furnace's life span.

Basement Ducts

• It is common for homeowner's to plug basement supply ducts because they feel the temperature is too cold. This lack of heat is due to the natural effect of cold air sinking to the lowest part of the house. If all of the ducts in the basement are filled, the space no longer gets proper airflow. This leads to a musty smelling basement because the air is stagnant and the moisture that accumulates in the lowest area of the house is never removed. In severe cases, it can lead to mold growing in the wall system.

Temporary Duct Fill

• During different seasons, homeowners fill ducts temporarily to increase conditioning in other parts of the home. One method to accomplish this is by closing the levers on the individual floor registers. If you want to completely close off the duct, remove the register cover and push an old shirt or sweater into the ductwork. Don't push the material too far into the duct; otherwise, it'll be difficult to remove it in the future.

Permanent Duct Fill

• If you are removing conditioning permanently from a portion of the home, you can cap the end of the ductwork. Place a properly sized duct cap over the end of the duct, and secure it with three or four self-taping metal screws. Seal the joint between the cap and the duct with aluminum foil duct tape.