How to Install Ducted Air Conditioning

An air duct in the ceiling.
What You'll Need
Flex duct/duct board
Duct connectors
Foil tape
Razor knife
Zip ties
Tape measure

The method by which most homes receive cool air is through ducted air conditioning. Ducted air conditioning is simply a network of air passages (i.e.: ducts) in an attic that supply air from an air handler to vented outlets in each room. Installing ducted air conditioning can be done using the following steps.

Step 1 - Select Air Duct

There are a few different kinds of air ducts available. Sheet metal ducts are rectangular, typically found in commercial applications and relatively inexpensive. They are, however, noisier and more susceptible to air leakage and condensation. Spiral ducts are round metal ducts that can be bent to different angles. The most common and effective duct system is insulated ducting. Insulated ducting is made as fiberglass duct board or flex duct. Both have insulation lined with a foil on the outside. Duct board is usually selected for the main duct work. Air is then transported to each supply vent through flex duct hoses.

Step 2 - Determine Design and Quantity

It is an enormous help to have a sketch or design of your intended ductwork. This is because you need to consider the number of rooms you are supplying air to, the distance to each room, and how the air will travel. You will be purchasing both duct board and flex duct. Having a design will help with calculating measurements so you know how much of each duct to purchase.

Step 3 - Install the Duct

Using your design, begin by cutting any main duct work. It is recommended you use duct board. Measure sections with the tape measure. Cut using the razor knife. The duct is constructed like a box, with foil tape attaching the ends. After you have constructed the initial section of duct, you can attach it to the air handler. Support the other side of the duct with a box or some other object to hold it even. Now cut an opening to accommodate the diffuser on the air handler. Tape around the edges with foil tape. You can now go to the other end of the duct and install a hanger. Nail one end of the hanger to a rafter or other support. Now wrap the other end around the duct and pull it up as needed. Nail the other end. Connect remaining sections of the duct board with duct connectors or collars. Tape around the edges. Add additional hangers as needed.

When the main ducting is complete, you can run the flex duct to each room's supply vent. Attach the flex duct to the duct board with a duct connector and a zip tie. Tape around the edges as needed. Now attach the other end to a metal diffuser and tape around the edges. Insert the diffuser into the ceiling hole.

Step 4 - Test the Installation

When complete, run your air conditioning. Check to see that air is coming out of each room's supply vent. Also inspect duct connections for any leaks.