Venting & Combustion Air

Category I against Category IV, vent sizing, and why a high-efficiency swap changes the chimney.

5 articles

• Furnace Venting — Why an 80% Uses Metal and a 96% Uses Plastic

  The pipe leaving the furnace is not an accessory. It is a consequence of how much heat the furnace took out of the exhaust.

• Where the Vent Comes Out — Clearances That Cause Real Failures

  A condensing furnace vents out the side of the house, and where that pipe ends is a code question with practical consequences every winter.

• The Condensate Drain — A Small Pipe That Shuts Down the Furnace

  The highest-efficiency furnaces are stopped most often by the least sophisticated part of them.

• The Orphaned Water Heater — What Happens to the Chimney After the Furnace Leaves

  The chimney was sized for two appliances. Take one away and the other one has a problem nobody mentioned in the quote.

• Water Dripping From the Furnace Vent — Normal on One Type, a Fault on the Other

  The same drip is expected on one furnace and dangerous on another. Which one you have is decided by the vent material, and you can see it from across the room.