Venting for high efficiency gas furnaces materials due to the condensing nature of a high efficiency furnace its venting must be made of a material that is resistant to corrosion.
High efficiency furnace exhaust pipe.
Low flue gas temperatures allow for pvc flues instead of metal.
The pvc pipes are used for air intake exhaust gas and to remove the corrosive condensation resulting from the combustion process.
Some high efficiency furnaces also include a plastic pipe for intake area and all types use a third plastic pipe to drain away the corrosive condensation resulting from the combustion process.
If you are unsure if you have this style the big clue is in the venting.
If the flue is made of pvc pipe you have a high efficiency furnace also called a condensing furnace.
Other aspects of high efficiency furnace venting.
In contrast modern high efficiency condensing furnaces exhaust much cooler gasses and need only plastic pipe materials such as pvc cpvc or abs for their exhaust vents.
New high efficiency furnaces can have efficiency of about 95 percent a huge savings for your wallet.
It is classified as type bh venting.
There are several other important aspects of high efficiency furnace venting.
These pvc or cpvc pipes can be inviting to rodents and birds especially in the winter as well as insects mostly in summer looking for a home.