Why is insulation important for gas furnace ducts?

Insulation is crucial for gas furnace ducts primarily because it prevents heat loss as air travels through the ducts. When heated air moves from the furnace through the ductwork to the living spaces in a home, it can lose temperature if the ducts are not adequately insulated, especially if they run through unconditioned spaces such as attics or basements. By insulating the ducts, the warm air retains its heat, leading to more efficient heating and reducing the energy cost associated with lost heat. This ensures that more of the generated heat reaches its intended destination, contributing to overall energy efficiency and comfort within the home.

While sound absorption and airflow resistance are also important factors in duct design, they do not address the primary function of insulation in maintaining the temperature of the air as it travels. Additionally, reducing the weight of the ducts is not a primary concern in the context of insulation's role.