I'm replacing the thermostat in my home and there is a separate step for "high-efficiency furnaces that are greater than 90% efficiency"

I have a furnace that is power side-vented with a PVC pipe. Is this the same thing as a high-efficiency furnace? Google searches bring up systems that are side-vented like mine, but I find a clear answer if all side-vented systems are considered high-efficiency.

  • Your furnace is power vented out the side and uses pvc? I think you may possibly be crossing terms. Can you list the furnace manufacturer and model? Also, not all direct vent furnaces are created equal, and if I'm not mistaken, "high efficiency" is considered 92% and up these days. Nonetheless, it is sounding like your unit, being side vented is possibly efficient, we just need to know about the POWER + PVC comment as that is possibly a big issue in one way or another. How long is the run out the side and how many bends?
    – noybman
    Commented Sep 24, 2017 at 21:21
  • I meant "power vent" in that there is a fan on the furnace that requires an electric outlet and blows waste air through a PVC pipe and out the side of the house. Commented Sep 24, 2017 at 22:22
  • 1
    alright, the fact the fan is on the furnace is a good thing. it is not unheard of that someone do something wrong. You'll still get a more definite answer if you provide model #/make. Given you are saying it is pvc power vented and the implication is that it is a proper install, then your unit is almost certainly efficient. But you'll have to look at the manufacturers spec regardless because not all furnaces are equal. And the actual answer is NO, not all side vents are high efficient. (but they usually use metal duct).
    – noybman
    Commented Sep 24, 2017 at 22:32
  • Does your furnace have a condensate drain and neutralizer? Commented Sep 25, 2017 at 2:02
  • PVC could only be used for inlet or exchange air, not exhaust. That practically implies the presence of either a heat exchanging air changer, or at least drawing combustion air from outside rather than consuming interior air and relying on the house to be drafty. Commented Sep 25, 2017 at 16:09


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