Which of the following materials is commonly used for venting in high-efficiency furnaces?

High-efficiency furnaces are designed to use modulating combustion technologies that significantly reduce the temperature of flue gases, which allows for the use of different materials for venting. Plastic pipe is commonly used for this purpose because it is lightweight, resistant to corrosion, and can effectively handle the cooler exhaust produced by high-efficiency systems.

These furnaces typically generate condensation as part of their operation, so materials that are not prone to corrosion and can withstand the acidic properties of condensate are essential. Plastic venting, often made of PVC or CPVC, fits this requirement very well. Unlike metal ducting, which may not be suited for the lower temperature flue gases and can rust or corrode over time, plastic pipes can maintain their integrity under these conditions and are easier to install.

Other materials listed, such as fiberglass and vinyl tubing, do not have the same compatibility with the exhaust characteristics of high-efficiency furnaces. Using the appropriate materials for venting is crucial for safety, efficiency, and longevity of the furnace system.