Duct Booster Fans

Overview

If a ductwork system is properly designed and installed, a fairly even space temperature should result. However, often rooms furthest from the heating (cooling) system don’t get enough air distribution to adequately heat (cool) them. This is typical with rooms that have been added on, have more than 2 exterior walls, or a lot of glass area.

Assuming the central system has enough capacity (the rest of the house is at the right temperature and the central unit cycles off and on during temperature extremes) a duct booster fan could resolve the problem.

Operation

A booster fan is installed inside the supply duct that runs to the space that needs help. It is a small electric fan that will increase both the total supply and the velocity of conditioned air to the space. It is turned on by either wiring it with the central furnace fan, a manual wall switch, or an automatic pressure switch.

Other Considerations

There are other things that could be making a space too hot or cold that a booster fan alone will not be able to resolve. This includes:

If the central system is undersized, it simply doesn’t have the capacity to serve the space. This could be indicated by a unit that never shuts off during temperature extremes, and yet the space does not maintain the desired temperature.
If the space has a lot of glass, especially poor-fitting windows, more air should help, but not eliminate the problems.
If the space does not have adequate RETURN air. In order for air to circulate, it must have both a supply AND return. Without both, the air will stagnate.

More Information

Duct Cleaning

Duct Insulation

Source: Text Bob Fegan 12/2008;