How to Make a Homemade Duct Fan for Ventilation

Look at the side of the 1 foot duct section. Looking at the side of the duct, mark the center of the duct and draw a ring all the way around the center perimeter of the duct. Use the hack saw to cut a small, 1-inch slit into the side if the duct. Move to the other side of the duct and cut another 1-inch slit. These slits should be cut so that when the metal bar is inserted through both slits, the bar goes through the inside center of the duct. This bar will be used as a mounting bracket for the motor and fan.

Bend the extra ends of the metal bar along the side of the duct and drill two 1/8-inch holes through both the metal bar and the duct. The first hole should be 3/4-inch from the 1-inch slit. Place the second hole 1-inch from the first hole. Insert and tighten two 3/16-inch screws on each side of the duct. This will keep the metal bar from moving.

Look inside the duct at the metal bar. Measure the length of the metal bar inside the duct and mark the center of the metal bar. For example, if the inside length of the metal bar is 6 inches, then the center of the bar is located at 3 inches. Next, look at the motor and fan assembly. A motor and fan assembly is used because the fan is already designed to work with that specific type of motor. Measure the distance between the motor mounting holes on the motor. Divide the resulting number in half. For example, if the mounting holes are 2 inches apart, then half of that is 1 inch.

Take the 1 inch from Step 3 and measure 1-inch from the center of the metal bar on each side. This tells you where to drill the mounting holes on the metal bar for the motor. Before drilling the holes, hold the motor in position inside duct up against the metal bar. Align the motor and the marked hole positions. When the fan is in the correct position, the fan should be 1/2-inch away from all sides of the duct. Mark the position of the mounting holes against the metal bar.

Drill two 1/8-inch holes into the metal bar. Use screws to attach the motor to the metal strip. These screws will hold the fan and motor onto the metal bar. Drill a small hole in the side of the duct to allow you to pull the fan motor wires out of the duct. Add expanding foam sealant or caulk to hold the wires in place.