As many contractors attest, a supply air plenum is a sheet metal box attached to a furnace or air handler’s outlet and is used as a central manifold connector for other ductwork. As the air blows from ...

[Editor’s note: When we last visited with lead installer John and his helper Charlie (The NEWS, March 5, 2007), they had just learned the hard way that there’s a lot more to sealing ducts than just ...