What is the preferred method for sealing metal ductwork?

The preferred method for sealing metal ductwork is UL 181 Mastic. This is due to its strong adhesion properties and ability to create a durable, lasting seal that can withstand the thermal expansion and contraction commonly experienced in duct systems. The mastic is specifically designed for use in HVAC applications, ensuring that it maintains its effectiveness over a range of temperatures and does not degrade over time.

In addition to its durability, UL 181 Mastic offers excellent flexibility, which is essential for accommodating movement in ductwork without compromising the seal. This method also minimizes air leakage, thereby improving the overall efficiency of the HVAC system and reducing energy costs.

Other methods, such as ultrasonic welding, while effective for certain applications, are less common in sealing metal ductwork due to the requirements for specialized equipment and technical skill. Silicone sealants, while versatile, may not provide the same level of adhesion and durability specifically required for duct applications as UL 181 Mastic. Foil tape, although widely used for quick repairs, is often not as reliable over the long term compared to mastic, especially in areas where a strong bond is critical. Therefore, UL 181 Mastic is recognized as the best practice for achieving optimal performance and longevity in sealed metal ductwork.