How to Install Sheet Metal Ducts

Map out the entire duct system before trying to install it. This will give you plenty of opportunity to scope out possible hazards including water lines, electrical boxes and structural supports. This also allows you to purchase only the duct work you need.

Take the duct pieces out of the box and assemble them. Cylinders will come fully assembled but rectangular duct comes in two pieces and must be clipped together with cleats.

Attach the first piece of duct work to the forced air unit or the trunk of an existing duct. Use sheet metal screws and duct tape to assure a tight seal.

Hang the remaining duct work according to your schematic. Make sure to keep a minimum of 1-inch clearance from any flammable materials. If there are structures you cannot avoid, you must cut and collar them, and be sure to seal the collar with duct tape.

Connect each piece of duct to the next with a slip connector. This coupler can be connected with sheet metal screws or duct tape. The tape creates an air tight seal and should be used whether or not screws are.

Install duct hangers every three to five feet. Screw these directly into wooden supports.

Seal every connection with aluminum foil tape or silicone caulking. This is extremely important because leaky air ducts cause inefficiency which can cause higher heating and cooling bills.

Add insulation around the duct work in areas that have large temperature deviations like the attic and basement.