I'm just a homeowner like yourself. I'll tell you what I've learned.

The picture seems to indicate the furnace is behind the viewer. Does the circle show where the existing grille is?

The galvanized steel shown makes the joist cavity into a plenum. If that plenum runs straight back to the furnace, you could consider crossing over at the furnace to the preferred cavity. Sheet metal work would be required to create the crossover. Were there any past or any planned future modifications that make this a good choice, or is it overkill.

Your mechanical contractor will probably tell you that he can create a single crossover where the circle is. Sheet metal is best but they can also seal off that part of the cavity and run flexible duct across. The expert will ensure the draw is balanced. The limiting factors on any install in addition to cost are appearance and headroom. Appearance and headroom are the reason for suggesting the first option.

The expert may also surprise you and say "hey, since you're moving this wall, I can just enlarge the grille over here, results just as good for less money" or something else we would not have considered.

If you're tackling this yourself be sure to read up on codes. Duct work is influenced by electrical and plumbing. For example wiring inside that cavity cannot just be Romex. A DIY-er could probably seal the cavity and run two elbows across from one to another, and not violate any code.

Again, I'm just a homeowner. Good luck.

Is there any other wall under that return run that you could relocate the vent to? That might be the easiest solution.

We also had a return vent issue in our kitchen remodel. It was in a pony wall that we were going to remove and it would have been too hard to move it elsewhere. Our solution was to build it into our island. An extra tall base for a bookshelf, on the end of the island, was fitted with a decorative vent cover.

Another possibility might be to put the return vent in the floor. We have one in fitted into our hardwoods, in one of our hallways.

{{!gwi}}