In tearing things out for the bath rehab, I uncovered some rotted 10″ x 3-1/4 duct work under the floor (currently under the OSB above)…that goes to nowhere. A patch in the bathroom floor (where the fancy grate is sitting above) indicates there used to be a boot on it and a floor vent. Now, the heat for this room is served off a separate duct that goes only to this room (see the grate to the right).
The dead-end duct is a 90° off the run that feeds a floor vent in what will be the guest bathroom, and did (and will again) continue up to a single boot/vent on the third floor.
The run up to the third floor was slapped on the outside of the wall in what will be my shower.
So, having already torn off most of the plaster, I plan to run new (non-rotted) 10″ x 3-1/4″ duct in the wall up to the third floor, which will necessitate building out that currently 1-3/4 deep wall a bit before putting up Wonder Board. I have to build it out anyway to fit the plumbing.
I doubt there’s any issue with replacing the straight run and the boot in the “new” bathroom and on the third floor.
But here’s my question: Is it acceptable to replace that (currently dead-end) 90° run to the old bathroom, attach a boot and move the floor vent back to where it clearly was before, thereby having three boots/vents on that one run? (Any issue from an HVAC standpoint, I mean…I do realize the vent location in front of the walk-in shower is not ideal, but it would solve another problem.)
The problem it would solve is to get rid of the ductwork currently serving the old bathroom. That run was slapped on the outside of a wall in my pantry, and when I redo the kitchen (If I don’t give up on this crazy house project before then, that is), I’d dearly love to push into what is currently a full bath on the first floor (off the dining room, which is weird) to make what is now the pantry large enough to be a 1/2 bath (which is to say I can’t just bury the ductwork in that wall, because it would still be in the way of making the room larger).
That full bath on the first floor? It was once a butler’s pantry. And if I can figure out the HVAC problem, it will be again. Someday. Not soon.
Oh – and in case it helps, here’s the view in the basement of both of the runs in question.