I inspected a home today that has a 1987 Snyder General 80,000 BTU furnace (no power vent) that is exhausting out the side wall. It has a 3" single wall stainless connector vent, sections only taped together with foil tape (no screws), running along side of the 2x8 floor joists (within 1" at some points), exhausting out the rear wall with in 12" of two windows, and only 12" off the ground (I am in Minnesota). This house passed the Truth in Housing inspection and was checked out by a HVAC company just days before and the tech wrote everything was fine.
I have only seen stainless used on fireplaces before and they have always been double walled. I have not seen it on a furnace before. Are all of these things allowed because it’s a stainless connector vent?