How to Install a Duct Damper

A duct damper provides a way to control the amount of air flowing out of a specific air-supply register.

Locations of dampers vary, but they should be installed as far away from the register as possible. This prevents noise at the register from the increased velocity of the air being squeezed through the smaller space that's created by the partially closed damper. Installing a duct damper requires a little bit of sheet-metal knowledge, but it's not a complex process.

Disconnect the duct at the joint where you want to install the damper. Remove all the sheet metal screws with a cordless drill. Pull the two pieces of duct apart.

Slide one piece of duct slightly sideways to gain access inside. Drill a 3/8-inch hole through the bottom of the duct, six inches in from the end.

Insert the damper into the end of the duct. Position it so the threaded prong sticks out through the hole you drilled.

Place the damper handle over the threaded prong, on the outside of the duct. Screw the included wing nut onto the prong to secure the handle and damper to the duct.

Slide the two pieces of duct back together. Reinstall the sheet metal screws to secure the duct joint.

Adjust the damper handle to your desired position. When it is perpendicular to the duct, it is completely closed. When it is parallel to the duct, it is completely open.

Things You Will Need

  • Cordless drill
  • 3/8-inch drill bit


  • Choose a location for your damper that's at least 5 feet away from the register, but near a duct joint for easy installation. Make sure your damper is easily accessible for future adjustments.
  • Trial and error comes into play when adjusting your damper to its ideal position. Play with it until you find a setting that makes the room it serve feel comfortably warm.