Is My Duct Work Adequate for My Furnace?

Furnace Ducts

• In a typical home, heated air is directed from the furnace through a series of thin, ducts made of sheet metal that feed the air through a vent into each room. The design and condition of your duct work has an important bearing on the general energy efficiency of the furnace, and it is important to understand that because efficiency ratings listed on new furnaces do not take the efficiency of duct work into account. For example, if you buy a 90 percent efficient furnace, it might not actually operate at 90 percent efficiency if your duct work is in poor condition. According to the U.S. Department of Energy, inadequate duct work can account for up to 35 percent reduction in your furnace's efficiency.

Duct Adequacy

• The most important way to determine whether your duct work is adequate for efficient home heating is to inspect the duct work regularly for any damage or tears. The most common cause of loss of efficiency through duct work is heat loss through openings in duct work. Repairing any holes in your ducts is one of the simplest ways to keep your ducts adequate for efficient heating.

Insulation & Sealing

• Seal any openings using mastic sealant or metal tape. Avoid using duct tape. Despite its name, duct tape is not effective at sealing ducts -- it will only offer a temporary seal and degrades easily. Once all openings in the ducts have been sealed, air losses that make the furnace operate less efficiently will have been minimized.

Insulation

• Finally, insulating your ducts can vastly improve the adequacy of your furnace duct work. Insulation, which typically comes in rigid foam board, wrapped around the duct work, especially in unheated parts of the home, will further help minimize heat loss and will help prevent the buildup of condensation on the ducts themselves. Install the insulation according to the manufacturer's directions and check it regularly to verify whether it needs replacement.