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I am removing an interior non-load bearing wall and need to move an HVAC duct a few studs over. I am leaving a short wall near the exterior to accommodate the duct as well as to serve as an endpoint to some 24” deep kitchen cabinetry.

Ideally, Id like the duct as close to the exterior wall as possible. The upper section connects in the attic space so I don’t want to move it so far as to make the installation difficult (attic section will be insulated). Is there a minimum distance I need to preserve from the exterior wall to the ductwork or can it go pretty much anywhere on the inside, e.g right against the exterior wall in the last stud Space on the left, pictured? Thanksenter image description here

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  • I'm assuming you are referring to the current hole in the floor (where the gap in the sill plate is) as the duct location that you want to move?
    – TylerH
    Aug 25, 2020 at 1:02
  • @TylerH Yeah. There was a vertical duct that I already removed, just plugged the hole with some cloths and duct taped over to prevent debris from falling. The duct is a pill-shaped profile. Like a 0.
    – David
    Aug 25, 2020 at 1:24
  • I cannot take the wall off yet, unfortunately, as it is supporting kitchen cabinets on the other side that we need to keep for now. I'm going to attempt to move the ductwork with the wall in place.
    – David
    Aug 25, 2020 at 1:27

2 Answers 2

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There is no minimum for running hvac near an exterior wall.

In fact you can run hvac outside (my old house had hvac under slab) and you can certainly run hvac in exterior walls. There are extra insulation precautions and some loss of energy in these cases but you have to do what you have to do.

Your case isn't as extreme. In fact it isn't extreme at all because your hvac is inside of the insulated bubble albeit closer to the edge of the bubble. Meaning that the vents themselves will aid in the cooling and the heating of said bubble.

Addendum: Given the conversation about the lines in the attic I want to make two points.

  1. If you live in a hot summer/cold winter climate I would not run flex lines in the attic - rigid all the way.

  2. You need to WRAP your lines in the attic, not just bury them in blown in. You must treat an attic extension as you were running the lines outside - because basically they are.

And obviously we want the vents placed on the exterior because that is the coldest/hottest part of the house and the area that needs the most temperature control. No issue with your install.

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  • I wish I would seen your answer I would just up voted and not tried.+
    – Ed Beal
    Aug 25, 2020 at 4:29
  • Thank you! Yes, it made (common) sense to me, just wanted to make sure.
    – David
    Aug 25, 2020 at 5:07
  • Comment to the addendum. Thanks for the extra tip. The flex line is already there but it has a full vapor barrier with insulation. Going to handle it the way I commented on Ed's post. Full vapor barrier + blown stuff between joists. Unfortunately, I cannot replace this with a rigid tube as the other end is connected under a finished part of the house. I could rip the ceiling on the other end, and I might just do that when I remove the wall, however I will likely leave the flexi line as I'd still have to insulate the rigid line.
    – David
    Aug 26, 2020 at 3:54
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You can run the duct on the wall that won’t be a problem. If your trunk is in the attic The problem usually ends up With the roof line if you go all the way to the wall. With enough space above it can be done. If your furnace trunk is below you should have no problem.

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  • Yes, getting close to the roofline will be somewhat tricky, but not that bad. In the attic space that duct connects to the flex line with a vapor barrier that I would need to extend. Can't get to the other end of the flex tube so thinking of splicing it to another 3-4ft piece of flex line with a duct pipe and Malco TY34 zip ties. Thank you.
    – David
    Aug 25, 2020 at 5:12
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    Yes that is what I have done sometimes the metal work looks like a 1st grade kid designed it to get far enough from the load bearing wall roof line for flex but after that no problem to connect up.
    – Ed Beal
    Aug 25, 2020 at 13:43

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