Single-pipe system: The single-pipe, non-direct vent system is used where there is no real need for a separate combustion air intake vent. It provides a vent pipe for exhaust gases but uses unconditioned (not cooled or heated) air from the space around the furnace for combustion air.

What is the difference between direct vent and non-direct vent furnace?

Direct vent (two-pipe) vent system – This system uses one pipe to bring in outside air for combustion and another to remove exhaust gases. Non-direct (single-pipe) vent system – This system uses only one pipe to remove exhaust gases.

What is meant by direct vent?

Direct Vent – a two-chambered venting system that uses outside air for combustion, pulling air in through one tube and expelling emissions through the other. … Natural Vent (B-Vent) – a single chambered venting system that uses air from within your home for combustion and releases emissions through a vertical flue.