Balancing Your Rooms For the Upcoming Cooling Season

 In Home Care

Many homeowners that use central air conditioning systems in their home know which rooms are cooler than others when the AC is running. If you have access to the ductwork and dampers in the basement, there is an “Old Fashioned” method to adjust and keep the temperature at a constant.

We call this the “Adjust, Measure, and Repeat” method and it’s a simple way to balance your central heating system using the dampers on the ductwork:


There are usually two types of ductwork, the heat runs and the cold air returns.

Cold air return ductwork usually use the cavity of the rafters to bring the return air back to the furnace.  These are sometimes wider and gather the air from the interior walls of the home.  No adjustments needed on these for this project.

Most heat runs will go up through the interior walls for the second floor and on the first floor most ductwork is located near the outside wall of the room.  Some are insulated and most are round. These usually will have the dampers.

1 – Start at the furnace unit and follow the main ducts outward, looking for small levers on the side; these are the handles for dampers. Use landmarks, such as bathroom piping to keep you oriented as to the location of each room.

2 – Make note where these damper handles are located and to which rooms they run to. When the handle is horizontal, the damper is fully open, allowing maximum airflow. When the handle is anywhere between horizontal and vertical, the damper is slightly closed, reducing airflow.

3 – Place thermometers in the rooms that you would like to balance, away from registers and cold-air returns, and all at about the same height from the floor.  Keep your measurements consistent and the doors to the rooms open.  Make sure thermometers are calibrated and are showing the same temperature in the same room, before putting them in other rooms.

4 – Measuring the rooms is best when there is a large temperature difference between the outside and interior temperature.  It would be hard to take measurements of 72 degrees in the rooms when it is 72 degrees outside.  Turn on the air conditioning and open all the dampers, wait about an hour, and then check the thermometers. Is one room Cooler than the others?

5 – Partially close the damper in the duct that feeds that room by moving the handle one-third of the way between horizontal and vertical; wait an hour and recheck the temperature of the room. If the room measures about the same as the other rooms, you’re done. If it doesn’t, close the damper another third, wait another hour, and check the room again. You can also fine-tune airflow by adjusting the register.

6 – Repeat steps 2 through 5 for each room until you have the temperature balanced. Please note, when we say balanced… we mean that the main living areas and bathrooms are cooler than the bedrooms, or vice versa. It all depends on what you prefer.

7 – After you’ve achieved balance, go back to the ducts and use a permanent marker to write a S (for Summer) where the damper handle should be positioned for the cooling season.

8 – Repeat the process for the heating season, except write an W (for Winter) where the damper handle should be positioned.


Clint Pharo is a local HVAC Contractor in Madison, WI. He and his team of HVAC professionals at Pharo Heating & Cooling cover a broad range of services in commercial buildings, new home construction, and residential homes and locally represent Bryant Heating and Cooling Products. He regularly posts on his company’s blog at

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