How to Install Air Conditioning and Heating Ducts in Your …

The largest and least glamorous part of any home or office HVAC system is the ductwork. Without ducts to carry the heated and cooled air throughout the building, these systems can only heat or cool one room. With properly planned and installed ductwork, however, one HVAC air handling unit is sufficient to keep the temperature of a large house comfortable.

Obviously, the size of the air handling unit and the air conditioning condenser are important. They must be sized appropriately to provide enough airflow for the air volume of the home or office. Thus, a building with high ceilings needs a more powerful air handling unit and a larger condenser than one with normal 8-foot ceilings. In addition to the size of the HVAC system, this guide focuses on designing and installing the ductwork. Read on to learn how to install air conditioning and heating ducts in your home or office.

There are three basic types of ductwork used for homes and offices, with a fourth method that can be done for parts of homes, without any ductwork at all. The three types are sheet metal ducts, duct board, and flexible ducts. Metal ducts are traditional, but the most expensive, often needing to be custom fabricated to match the area. They are also not insulated, which causes them to lose heat into attics, ceilings, and crawl spaces. For this reason, duct board has largely replaced metal ducts.

Duct board is an aluminum foil-coated fiberglass insulation panel. It provides several advantages over metal, while being less expensive to install. The ductwork can be easily cut to size with a utility knife and shaped to meet the needs of the building, and is insulated.

Flexible ducts are used in conjunction with both of the other types of ductwork, predominantly to go from the main duct to individual heating and cooling registers. This makes the installation of these much faster and easier, reducing the overall installation time.

The fourth method, which is used only in homes, is to use the space in the walls or ceilings for ducts. By capping off a section between two studs with aluminum flashing, an instant duct is made. The same thing can be done in the floor joists. While quick and easy, this method depends on the framing of the house running in the right direction to be useful in this manner.

When laying out a ductwork plan, it is important to consider the return air plenum. The air handling unit pumps a large amount of air through the home or office. It needs a constant supply of air to heat and cool so that the air can be returned back to the living spaces.

The return air plenum needs to be located in a place where it is as far from the HVAC registers as is practical. It also needs to be located in a place where it is close to the air handling unit so that the unit does not have to work to pull the air into it. The air filter is located at the entrance to the return air plenum, and the thermostat is usually located close to it.

Most ductwork is installed in either the basement or attic of a home. For businesses and offices, it is installed above the suspended ceiling. This allows it to be installed in areas which are not occupied and are out of the way of traffic. It is usually best to install the ductwork once the building is framed in, but before the installation of drywall. Often, the ductwork is installed at the same time as rough electrical work.

If ductwork is installed in the basement, floor registers are usually used. If it is installed in the attic or above a suspended ceiling, ceiling registers are normally used. Each system has its own advantages. For more efficient cooling, an attic installation is better. For more efficient heating, a basement installation is better.

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How to Install Air Conditioning and Heating Ducts in Your ...