Mar 04, 2020 · High Efficiency Furnaces; Should you Two pipe vent or One pipe vent? admin Furnaces March 4, 2020 March 4, 2020 Fresh Air, Furnace, High Efficiency, Single Vent, Two Pipe, Venting 1 Comment Since the mid 1980's high efficiency furnaces have seen a popular growth in part due to government requirements to reduce energy cost and green house ...