Heating
What Is Condensing Furnace & Venting?
Definition
A condensing furnace burns gas so completely (95%+ AFUE) that the exhaust gas cools enough to condense into water before it leaves the house — cool enough that it is no longer safe to send up a hot metal flue. Instead it vents sideways through PVC pipe and drips condensate into a drain, the way a standard 80% AFUE furnace's hot exhaust never has to.
Why it matters for your home
If your furnace bid mentions new PVC pipe running out a side wall and a condensate drain or pump near the unit, that's this — not a mistake or an upsell, it's what a 95%+ AFUE furnace requires to vent safely.
What to do about it
Ask where the new vent will exit the house and whether a condensate pump is needed (it usually is if the furnace isn't near a floor drain) before the install date, not on it.
This definition is pending licensed-trade technical review. It's sourced from our own published service and guide content, not invented — but hasn't yet been signed off by a licensed HVAC reviewer.
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