Why Insulate Ducts in Basements?

Ductwork is often not insulated in basements throughout the Greater St. Louis Area. Why? A better question is, why not?

Homeowners often do not realize the importance of insulating the ductwork in a basement. The thinking goes that it's an unnecessary home improvement because the temperature in the basement is tempered throughout the year. 

The effects of outdoor and indoor temperatures

During the winter, outdoor temperatures may be freezing but the temperature in the average basement will not be much lower than the temperature upstairs. During the summer, outdoor temperatures may be scorching hot, but the temperature in the average basement is the same or even lower than the temperature upstairs. In either case, the ductwork is not exposed to outside temperatures.

Another aspect of temperature differences within a home exists between the air in the basement and the air inside the ducts. In the wintertime, the heated air produced by the typical furnace is around 120 degrees. Once that 120 degree air enters the system of ductwork, it begins to cool immediately.

Leaky and un-insulated ductwork often makes for an uncomfortable home...

If the air in the basement is 65 degrees, the metal ductwork is likely to be approximately the same. That means a 55 degree temperature difference will exist between the basement air at 65 degrees and the heated air from the furnace at 120 degrees. Overcoming the 55 degree temperature difference can require a large amount of heat.

Often, by the time the heated air passes through the system of ductwork, a significant amount of heat has been lost. The heat intended for any particular room of the house may be lost in the basement. That room may be uncomfortable in the winter if enough heat does not reach it before the thermostat located in another room is satisfied, and the furnace shuts off. 

The room may be just as uncomfortable in the summer due to cooling losses through the same, uninsulated ductwork.  Insulating ducts in basements can help make uncomfortable rooms comfortable in both winter and summer.