What material lines the interior of Type L vents?

Type L vents utilize stainless steel for their interior lining. This material is specifically chosen due to its excellent resistance to corrosion and high temperatures, making it suitable for venting appliances that produce flue gases, such as furnaces, boilers, and water heaters. Stainless steel's durability enhances the longevity of the vent system, ensuring that it can withstand the rigors of temperature changes and the potentially corrosive nature of the gases being vented.

While galvanized steel is often used in other venting applications due to its protective zinc coating, it may not provide the same level of heat resistance or longevity in high-temperature applications as stainless steel. Fiberglass, although used in some insulation applications, does not have the structural integrity needed for a venting system, which requires a robust material to handle both high temperatures and the passage of flue gases safely. Cast iron is quite heavy and not suitable for venting applications as it does not provide the flexibility or the necessary corrosion resistance compared to stainless steel. Therefore, stainless steel is the optimal material choice for the interior of Type L vents.