Dear Jim: We have a problem keeping everyone comfortable. Some rooms are always too warm (especially on the second floor) and others too cool. What can we do to get more cooled or heated air to the problem rooms? – Patti W.

Dear Patti: I had the same problem in my own two-story home, but uneven room temperatures also are common in one-story homes. Differences in duct lengths, number of windows, orientation to the afternoon sun, etc. can affect individual room temperatures.

Not only is it uncomfortable, but uneven room temperatures can increase your utility bills. You invariably set the thermostat too low or too high so the problem rooms are comfortable. For each degree you lower your air conditioner thermostat during the summer, your utility bills can increase by 2 to 5 percent.

The method I used to solve the problem in my home was a combination of adjusting the duct dampers and installing duct and register boosters where needed. Using an expensive automatic duct zoning system is the ideal solution, but it typically costs thousands of dollars to install one.

There should be adjustable damper plates in the ducts leading to each room. During the summer, make sure the dampers are fully open to the problem rooms that are too warm and close the dampers slightly to the rooms that are cool enough. This will force more cooled air to the problem rooms.

Don’t close any of the dampers more than halfway; this may cause too much overall airflow resistance for the blower. If the airflow is greatly reduced, the air-conditioner coils will not operate efficiently. During the winter, you probably will have to readjust all the dampers.

Most likely you also will need some booster fans. Ones that snap over a wall or floor register draw more cooled or heated air into the problem rooms without reducing efficiency. These quiet register booster fans are attractive and have built-in adjustable controls for summer or winter operation.

Another option is in-line duct booster fans. These fans mount in the ducts that lead to the rooms to increase the airflow. They are available in many diameters for simple installation in any duct.

If there is a problem with temperature variations in adjacent rooms, try installing a room-to-room door fan. These small, quiet fans mount in the upper corner of a door opening to circulate air from one room to another.

Installing adjustable floor registers is an alternative to adjusting duct dampers to control the airflow. The natural wood or ornamental cast-iron ones also are very attractive. Others have built-in air filters for better air quality.

Write for (instantly download – www.dulley.com) Update Bulletin No. 486 – buyer’s guide of 14 automatic register-duct booster fans, filter and decorator register manufacturers listing sizes, airflows, colors, features and prices. Include $3 and a business-size SASE, and send to James Dulley, 6906 Royalgreen Drive, Cincinnati, OH 45244.