Balance Ductwork for Air Conditioning

The air registers throughout your home control the amount of air going into each room. By closing the dampers in rooms you don’t want to cool with AC, you can save some energy and money.

The air registers throughout your house have little dampers (flaps) attached to controls on the registers — usually a handle or wheel. As a general rule, the best way to cool a house is to close the ones in the basement and open the ones on the top floor.

Time — 5 minutes per room
Difficulty — Easy
Expertise — None
Frequency — Once a year
Where — Regions with warm summers

Steps

1. Close the dampers on registers in rooms that you don't want your AC to cool.
   • Closed dampers are not terribly airtight. To really stop airflow to a specific area, remove the register and stuff a rag into the duct or cover the opening with a piece of cardboard and duct tape before reinstalling the register.
   • If you have high and low return air registers, close the bottom ones to draw the warmer air from near the ceiling back to the AC.
2. Open dampers in rooms you want to cool in summer.
3. Test the airflow of open registers. Put your hand in front of a supply air register to gauge the amount of air coming out. For return registers, test by holding a facial tissue in front of them — it should be sucked against the grille.

Tips

• If you usually keep the door closed to a room that has no return air registers, cut an inch off the bottom of the door to allow cool air to escape.
• Balancing dampers within the ductwork can be changed from season to season, but it requires some expertise. If you have it done professionally the first time, have the technician install handles on the balancing dampers and mark the positions for heating and cooling with a marker. That way, you can do it yourself in the future.
• For a house to feel comfortable, set the AC to 10 degrees cooler than the outdoor temperature.