How to Control Air Flow in Attic Ducts

Posted by Lori Lapierre on 10th Feb 2014

Adjusting the temperature in a house can be difficult; rooms facing the sun are naturally warmer than other rooms in the house, and finding a balance -- especially during change seasons -- can be tricky. The biggest chore is adjusting the air flow valves known as dampers in the ductwork; and when the ductwork is in an attic, fine-tuning the process can be a system of trial and error, demanding time and patience.

1. Turn the lever on all the registers inside the house to the full open position. These can be closed later to adjust air flow to a desired level.

2. Open the door or access panel to the attic and examine how much lighting is available. Turn on any electric lighting or open curtains if the attic has windows; take a flashlight with you for any work that requires brighter lighting.

3. Go into the attic and follow a duct from the furnace to find the damper inside of the ductwork. It will be controlled by either a lever, or a small rod that can be adjusted with a screwdriver and fits into a wingnut. The dampers are usually located where the main duct connects with a round supply duct going to various areas of the house.

4. Turn each damper to the full open position. If this is a lever, it should run parallel to the ductwork. If it is a rod, use a screwdriver to adjust the rod until air is moving through the duct at the highest level.

5. Go into the house and test each register to determine how much air is coming into each room, and return to the attic to adjust the pertinent damper. If you are unfamiliar with which damper goes to what room, this may take several attempts before the desired result is achieved.

6. Use a marker to write on the ductwork which room it services, and what position the air damper should be in for optimal air flow. This will save time later from repeating the process if the dampers have to be adjusted seasonally.

7. Close or open the registers in each room to fine-tune the temperature once the duct dampers are in the desired position. Close off any registers for rooms that are seldom used to save on energy costs.