I had sweating ducts.i pulled the drywall down and wrapped all the ductwork.the main stack, two 4 inch ducts and two 6 inch ducts in my dining room and into the kitchen. I got to one spot where the two 6 inch ducts go through the main truss in the center of the house. The builder put a third truss butt up against the main support truss but they did not line up the openings. They squished the two 6 inch ducts down to about 2 inches to get through the opening. I don’t have anywhere I can rerun this. Can I put put a Y pipe on the two 6 inch ducts to reduce it to one 6 inch pipe then put another Y pipe on the other side to go back to 2 ducts?


You can...but do you need to?

If you have a square duct, 4x4", it has a cross section of 16 square inches.

If you squish it to 2x8", it still has a cross section of 16 square inches.

I think it's good the way it is and you aren't losing any airflow.

  • Thank you for answering. It makes sense, the only problem is because the builder squished two 6 inch ducts through the opening. It leaves no room to wrap insulation around it. The wood and drywall are wet from the sweating ducts. Everywhere else I wrapped seems to have stopped the sweating. If I don’t wrap this area, it will continue to drip. – Jim Sep 9 '20 at 23:16
  • I understand. Maybe spray foam? – Steve Wellens Sep 10 '20 at 4:42

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