How to Install HVAC Supply Ducts in the Basement

HVAC supply ducts transport warmed or cooled air from the furnace to each supply air register in the home. For whatever reason, you may want to add another supply air register into a room. To do this, you'll need to install a new HVAC supply duct from your main duct trunk to the supply air register boot. A boot is a 90-degree fitting that connects to the supply air register and the supply duct. Installing HVAC supply ducts requires a few simple sheet metal tools.

Step 1

Measure the distance from the main supply duct trunk to the supply air register boot. Plan an installation route for your ductwork.

Step 2

Cut out a circle in the main supply duct trunk in a location that will allow you to install the ductwork with the least amount of elbows. The circle diameter should match the diameter of the duct you are installing.

Step 3

Insert the tabbed portion of the sheet metal collar into the hole and fold over the tabs to lock the collar into the ductwork.

Step 4

Connect the first piece of duct to the sheet metal collar. Slide the non-crimped end over the collar up to the bead. Secure it with four sheet metal screws.

Step 5

Install the ductwork until the system is connected from the collar to the supply air register boot. Make each connection by sliding the non-crimped end of one piece over the crimped end of the previous piece. Secure each connection with four sheet metal screws.

Step 6

Cut down the duct as necessary when shorter pieces are required. Use your snips to cut the duct down. Add a crimp to one end with your pipe crimper so that it can be connected into the duct system.

Step 7

Add support to your ductwork if the length exceeds 5 feet. Screw a piece of galvanized hanger strap into a ceiling joist, wrap it around the duct and screw the other end into a ceiling joist. The hanger will resemble the letter U and the duct will be cradled in the middle. Hangers should be spaced every 5 feet.


  • Wear gloves when working with ductwork. The metal edges are very sharp and will cause serious cuts if your hands are not properly protected.