B-vent condensation in large attic space
You could add a fiberglass pipe insulation to the flue pipe to keep the flue gasses hot enough to prevent them from condensing. I had the same problem with the vent from my water heater so I covered the &quot;B&quot; vent with 1-1/2&quot; thick fiberglass pipe insulation. The flue gasses no longer condense and the flue works great.