What material is commonly associated with high resistance among duct types?

The material commonly associated with high resistance among duct types is paper-fiber. This type of duct is utilized primarily in low-velocity systems and is known for its excellent thermal insulation properties and sound attenuation. Paper-fiber ducts can be less conducive to airflow compared to other materials. The high resistance to airflow is a notable characteristic, which makes it ideal for applications where reducing noise levels and maintaining temperature is crucial.

In contrast, other materials like galvanized steel, aluminum, and plastic usually exhibit lower resistance, allowing for more efficient airflow in a system. Galvanized steel and aluminum are often chosen for their strength and durability, which provide reliable options for high-velocity systems where airflow is critical. Plastic ducts can be lightweight and easy to install but typically do not provide the same level of insulation as paper-fiber ducts in terms of sound and thermal resistance. This highlights the unique role that paper-fiber plays in specific ducting applications where resistance is a key requirement.